by an ochre-yellow line, each side between the eyes adjacent to them is an abruptly elevated, rufous tubercle; the mesial carinate line feeble, becoming obliterated posteriorly; humeri elongate-tuberculate, quite prominent; pleuræ darker than the pectus. Legs robust, brownish-ochreous. Hemelytra milky-white, as long as the abdomen, the nervures brownish-ochreous. Tergum pale ochreous, brown at base, the sutures and lateral raised edge brown; connexivum with a silvery, depressed dot adjoining each suture, the apical processes robust, of medium length, hardly acute. Venter smooth, dark ochreous.

Length to tip of processes 17 millims. Breadth across humeri 3 millims.

Corixa decolor, n. sp.*

Pale testaceous, dirty amber yellow above. Form of C. hieroglyphica Fieber, of Europe. Head large, cranium very convex, prominent, carinate on the middle, the vertex acutely produced. Face very deeply, concavely excavated, the cavity broad oval, occupying the whole width between the eyes and extending from near the upper edge of the eyes to the base of the clypeus, the middle of the excavation densely clothed with silvery hairs. Pronotum narrower than the head, almost twice as broad as long, the middle line feebly carinated anteriorly; the surface minutely rastrated, with about eight transverse, slender brown lines, each bounded in front by a faintly impressed line, the anterior line interrupted, the posterior one following the margin of the pronotum; the posterior margin triangularly rounding, extending pretty far back. Pleural pieces whitish; sternum honey-yellow. Anterior legs short, wide, pale honeyyellow, their tibiæ broad, compressed, blade-like on the anterior margin, oblong-oval, but little longer than the palæ; palæ subtriangular, a little longer than broad, fringed with long white ciliæ; the basal angles prominent, feebly rounded, the inner edge a little concave, tip acute. Intermediate and posterior legs slender, paler than the anterior ones, ciliæ and pubescence

*The fact that bread is made by the Mexicans from the eggs of a brine-inhabiting Corixa is noticed in Westwood's "Classification of Insects." Prof. O. C. Marsh has informed me that these brine insects are also noticed by M. Virlet d'Aoust in the Bulletin de la Société Geologique de France, 1858, xv. p. 200, and also by E. B. Tylor in his "Anahuac," London 1861. The latter says "A favorite dish here [Tezcuco] consists of flies' eggs (Corixa femorata and Notonecta unifasciata, according to Menneville and Vielet d'Aoust) fried. These eggs are deposited at the edge of the lake, and the Indians fish them out, and sell them in the market place. So large is the quantity of these eggs that at a spot where a little stream deposits carbonate of lime, a peculiar kind of travertine is forming which consists of masses of them imbedded in the calcareous deposit."

The flies which produce these eggs are called by the Mexicans "Axayacatl" or water face. The eggs are sold in cakes in the market, pounded and cooked, and also in lumps au naturel, forming a substance like the roe of a fish. This is known by the characteristic name of ahua-uhtli," that is, "water wheat."

In this connection we may remark that, according to the late Mr. IIorace Mann, Jr., the Indians about Mono Lake eat large quantities of the puparia of Ephydra.

whitish. Hemelytra pale yellowish, the costal area whitish, the cross-nervule and a spot at tip brown; clavus at base with short, narrow brown lines running transversely from the outer and inner margins, beyond the middle to tip the lines run completely across; lines of the corium transverse, slender, slightly waved, many of the intermediate ones entire; membrane pale brown, with short, vermiculate, white lines. Venter and metasternum faintly dusky, the connexivum and genital segments whitish.

Length 44 millims. Breadth across the pronotum 14 millims. This species must be closely related to C. Burmeisterii Fieber, of Europe. The shape of the palæ and markings of the hemelytra of our species do not agree with Fieber's description. The specimen described is a male, which appears not to be fully

mature.

From Clear Lake.

MARINE INSECTS FROM DEEP WATER.

During his explorations at Eastport the past summer, Prof. Verrill dredged at the depth of 20 fathoms in Eastport harbor a larva of Chironomus oceanicus Pack. (Proc. Essex Inst., vol. vi, p. 42). It does not differ from specimens found by me at lowwater mark in Salem harbor. It is evidently the same as the supposed larva of Micralymma?, mentioned and rudely figured in the American Naturalist, vol. ii, p. 278, found by me many years ago at low-water mark in Casco Bay. It is of the same size as the Salem specimens, being 25 inch in length.

Thalassarachna Verrillii n. sp. (Fig. 5; a, head and mandibles and maxillary palpi; c, under side; d, anterior claw. This

5.

XA A

species differs in important particulars from our best known species, Hydrachna formosa Dana and Whelpley (Amer. Journ. Sci., xxx, 354, 1836), found near New Haven, in fresh water Unionidæ. The body of that species is much longer, the

maxillary palpi are stouter and the relative length of the joints very different; the claws are very different, the forks of each claw being large and of equal size, and there is no brush on the base of the claw. At first I was disposed to place this halophilous species in the same genus as Dana and Whelpley's Hydrachna formosa and H. pyriformis, but having since then, through the kindness of Prof. Verrill, had the opportunity of studying a fresh-water mite closely allied to H. formosa, which is described below,* I am led to consider the salt-water mite as the type of a new genus, Thalassarachna, with the following differential generic characters; a conical head distinct from the rest of the body, maxillary palpi 5-jointed, each ending in an incurved spine, (the 5th joint). Mandibles large, forming an ensiform beak nearly as long as the palpi. Claws long, the upper hook minute, a single row of hairs on the under side of the lower hook, forming a brush. Otherwise closely allied to Hydrachna. The body is globular, convex above, with the abdomen obtusely rounded behind; the skin being minutely lineated. It is blackish when alive, with the head and edge of the body white. The head is minute, conical, subacutely pointed in front. The maxillary palpi are 5-jointed, a little more than twice as long as the head, and about one-fourth as long as the fore legs. The second joint short; the third joint one-third as long as the entire palpus; the fourth as long as it is thick; the fifth minute and carrying a long, slender, slightly incurved spine bifid at the tip, the outer fork projecting considerably beyond the inner one. The mandibles form an ensiform acute beak, reaching to the middle of the terminal palpal spine. The two eyes are remote black dots situated on the anterior fourth of the body, over the insertion of the second pair of legs and just in front of them is a well marked transverse groove crossing the body. The legs are 6-jointed, much alike in structure, moderately hairy. The claws are alike in size, the hook being moderately curved, rather

* Hydrachna tricolor, n. sp. Under this name I describe a beautiful mite, brought me from New Haven by Prof. Verrill after the present article was sent for publication. It is 07 inch in length, including the palpi. It is elliptical in form, a little broader behind, being two-thirds as broad as long. Ocelli situated over the insertion of the 2d pair of legs, the distance between them equal to half the width of the body. Body orange red, middle portion of the body black-brown, due to the color of the large liver, with a Y-shaped mesial line pale straw yellow in color, formed by the interspace between the two halves of the liver; the forks of the Y clavate. Appendages very pale grass-green. Legs much as in H. formosa, but the hairs are longer. Maxillary palpi the same as in H. formosa, there being two pairs of minute spines on the 4th palpal joints. Mouth and lancet-formed organ (languette) protruded as in H. formosa. "Bifid linguette" at the base of maxillary palpi, as in H. formosa. The rudimentary mandibles form a conical protuberance, the base situated within the body, each mandible being twice as long as broad, and reaching to the basal third of the 2d maxillary joint.

Twelve eggs, ten of them fully formed, being as long as the basal joints of the legs, could be seen on the under side of the body. The mite was alive Dec. 30, showing that the eggs, probably laid in the spring, are formed in the preceding autumn.

long, bifid at the end, the upper fork being much the smaller, especially on the anterior pairs, forming a small acute tubercle; in the middle of the under side of the claw (on all the feet) is a brush of fine hairs of equal length, arranged in a single row. On the penultimate joint of the anterior tarsi are five stout hairs; on the other tarsi three, the two proximal hairs being contiguous. External female genitalia with two bivalve contiguous plates, like those of H. formosa Dana and Whelpley. Length 07 of an inch. The body of the young is whitish, longer, more ovate than in the adult; the abdomen being a little pointed behind.

With the exception of Philippi's Pontarachna punctulatum (Wiegmann's Archiv, vol. vi, p. 191, 1840, Pl. iv, fig. 4, 5), which was discovered by him in the bay of Naples (he does not state at what depth, consequently I infer that it was in shallow water), the species under consideration is the only one which, so far as I am aware, has been found to be exclusively marine. The genus Pontarachna is very different from Hydrachna and Thalassarachna, and I should judge that it rather approaches Atax. It differs from Thalassarachna in the shorter, unarmed palpi, and in the apparent (Philippi does not mention or figure them) absence of a mandibular beak. The palpi are half as long as the fore legs.

The present species was dredged by Prof. Verrill in 20 fathoms, on Clark's Ledge, in Eastport Harbor. It was found (four or five specimens, young and adult), "on hydroids," &c. will be an interesting point to determine whether, like the other species of the genus, it also lives in the earlier, or even in the adult state among the gills of Lamellibranchs, and also whether it lives between tide marks, thus agreeing with the distribution of Chironomous oceanicus. At any rate we have here an insect and a mite breathing by trachea, and extracting the oxygen from the water at the great depth of 120 feet, and, in the case of the dipterous larva, with no apparent variation from specimens living at low-water mark. In this connection I might notice the fact that we have on our New England and Labrador shores several species of mites of the family Trombididæ, which run over seaweeds and live under stones between tide marks, and I have observed similar species at Beaufort, N. C., and Key West, Florida.

As regards the distribution of the species of brine insects, several questions of interest arise. How are we to account for the origin of the Ephydra halophila in such prodigious quantities in the vats of the Equality Salt Works of Illinois, a focality remote from salt lakes and the ocean shores? Are the brine

species of the Salt Lakes of Utah and California, remnants of an oceanic fauna, and of the tertiary period, or are they of re

AM. JOUR. SCI.-THIRD SERIES, VOL. I, No. 2.-FEB., 1871.

cent and local origin? Have these brine insects acquired their singular tastes within a recent geological period (say the Quaternary), having lived at first as do their allied species, in foul fresh water, or amid decaying matter in damp localities? Before these and other questions can be answered, we must have analyses of the waters, and a review of the European literature of the subject, and larger collections of brine animals from our own country.

*

Peabody Academy of Science, Salem, Nov. 16, 1870.

ART. XVIII-On the existence of the Nummulitic formation in China; by Baron VON RICHTHOFEN. (From a letter to Prof. J. D. WHITNEY, dated Su-Chan, China, Dec. 12th, 1868).

THE subject of this letter is the discovery of the occurrence of the Nummulitic formation in China, a fact which adds one more to the short series of formations known, chiefly by the labors of Mr. Pumpelly, to enter into the composition of this country.

Mr. Pumpelly cites, on the strength of a statement by Rev. Mr. Edkins, the island of Si-Tung-ting in Tai-hu lake (a sheet of water of about eight hundred square miles, sixty miles west of Shanghai), as a fossiliferous locality. As he learned that the fossils were found in limestone, he was naturally led to the conclusion that this rock formed part of the wide-spread Devonian limestone. Inquiries which I made in Shanghai confirmed the fact of the occurrence of fossils. There, too, they were considered as Devonian, and I was advised by a really skillful geologist, to study their mode of occurrence, as this would give me the clue for the structure of most portions of

*I am indebted to Mr. F. Walker of London for the following note on the habits of the English species of Ephydra and its allies. He writes under date of Dec. 6, 1870. "I have observed species of Ephydra along the sea shore as well as several inland aquatic species. I am indebted to my friend, the late A. H. Haliday, for the descriptions of the species of this and the neighboring genera in my Diptera Britannica, vol. 2. I am not aware that the species are very different in their habits, and he does not mention them as such. He writes of the following species as occurring on the sea shore.

Heccameda albicans, on sandy coasts, especially on fresh rejectamenta.

Hydrellia thoracica, on the sea coast.

Atissa pygmæa, in a salt marsh.

Glenanthe ripicola, muddy sea coast.

Scatella sibillans, sea coast.

Teichomyza fusca, on chalk cliffs a little above high water mark; swarms also occur in urinatories in London and other towns. Von Heyden, in the Entomologische Zeitung, Stettin, mentions Cania halophila as a sea-side insect. I believe that no European Stratiomys has been discovered to live as a larva in sea brine."