compressed; consisting of twenty-one segments--five cephalic, eight thoracic and eight abdominal. Carapace compressed, with, no regular hinge, loosely attached to the body by an adductor muscle; with a movable rostrum inserted in a depression in the front edge, the carapace covering the basal joints of the abdomen. One pair of stalked eyes; no simple eyes. Two pairs of welldeveloped, many-jointed, long, large antennæ, the first pair biramous, the second pair with a very long flagellum in the male. Mandibles weak, with a remarkably long three-jointed palpus. Two pairs of maxillæ; the first with a remarkably long, slender, multiarticulate exopodite; second pair well developed, biramous; no maxillipedes; eight pairs of biramous, broad, thin, respiratory, thoracic feet, not adapted for walking; the exopodites divided into a gill and flabellum; four pairs of large and two pairs of small abdominal swimming feet; no appendages on the seventh segment, the terminal one bearing two long caudal appendages (cercopoda). No telson present in the living species; well developed in the Ceratiocarida. Young developed in a brood sac; development direct; no marked metamorphosis; the young but slightly differing from the adult.

Remarks. By the sum of the foregoing characters the Phyllocarida appear to be excluded from any other group of Neocaridan Crustacea.

The differential characters separating them from the Decapods or any other Malacostracous type, are:

1. The loosely-attached carapace, the two halves connected by an adductor muscle.

2. The movable rostrum, loosely attached to the carapace.

3. The very long and large mandibular palpus; the long, slender appendage of the first maxillæ, and the very long biramous maxillæ.

4. The absence of any maxillipedes.

5. The eight pairs of pseudophyllopod thoracic feet, not adapted for walking; the animal swimming on its back.

7. No zoëa-formed larva.

The differential characters from the Phyllopods are the following:

1. Carapace not hinged; a rostrum present.

2. Two pairs of well-developed long and large multiarticulate antennæ; the hinder pair in the male longer than the first pair.

3. The thorax and its appendages clearly differentiated from an abdomen.

Internal Organs.-No functional shell gland; no highly-developed liver tubes like those of all Phyllopods; stomach and cœcal appendages (liver) entirely unlike those

of Phyllopods.

The nervous system is entirely unlike the Phyllopod type, and approaches more the Decapod and Tetradecapod type. The resemblance to the Copepoda is in

FIG. 12.-Echinocaris punctatus; abdomen, dorsal view, natural size. From Hall.

some points quite
striking; this is
seen in the equal
size of the two
pairs of antennæ,
in the form of the
abdomen, and the
two caudal appen-
dages,as well as the
spines on the hind
edge of the seg- sublevis.
ment, in the well-developed palpus of the
mandibles, in the absence of maxillipedes,
as well as the simple reproductive glands.

FIG. 10, Echinocaris multinodosus.

In short, we regard the Phyllocarida as an accelerated, prematurative type of Crustacea which became well established in the lowest Primordial period, flourishing at a time when there was no Malacostracous forms, and which culminated in the Upper Silurian period, and became nearly extinct at the close of the Carboniferous. Judging the group by the structure of Nebalia alone, whether we consider the external or the internal

structure, it is a highly composite or synthetic type, combining Copepod, Phyllopod and Decapod-like features with more fundamental characteristic ones of its own. The group existed at a time when, save in the Carboniferous period, no Malacostraca, or at least very few, existed, and they thus anticipated the incoming of the more specialized Decapods.

Like many other synthetic, ancient types, the fossil representatives were of colossal size compared with the living survivors.

While some of the fossil forms were of moderate size, though. very large compared with Nebalia, some must have been of gigantic proportions. For example, in Dithyrocaris neptuni Hall, of which Fig. 9 represents the telson and cercopoda of natural size, the entire animal must have been some two feet in length. The Echinocaris punctatus must have been nearly a foot in length, while the Echinocarides (Figs. 10 and 11), described recently by Mr. R. P. Whitfield, were considerably smaller.

:0:

AMERICAN WORK ON RECENT MOLLUSCA IN 1881.

BY WILLIAM H. DALL.

(Continued from November number.)

Psychology-Owing to the secluded life of most mollusks they are not easily subjected to long-continued observation, and perhaps for this reason notes on their affections or mental processes are nearly unknown. But that careful observation would reveal in many mollusks a much higher degree of intelligence than they are usually credited with, there can be little doubt. A small contribution to this subject is contained in the paper on "Intelligence in a Snail," by the writer (AM. NAT. Dec. 1881, pp. 976-7). The observations there noted indicate that some species of the genus Helix are capable of recognizing a call or sound, and of distinguishing it from other calls or sounds. Since this was printed the writer has had information of two other cases of the same kind, though the facts are less clearly indicated than in the one first mentioned. Dr. Lockwood's observations on Mytilus indicate a certain degree of intelligence, and it cannot be doubted that observations on cephalopods would show that these highly organized mollusks are capable of more or less complex mental operations.

Geographical Distribution and Catalogues.-In the Annals N. Y. Acad. Sci. (II, pp. 117-126) in an article "On the relations of the fauna and flora of Santa Cruz, W. I.," Bland shows, from a discussion of the land shells, that it is probable that St. Thomas and other islands of the Virgin group were formerly connected with Santa Cruz, but that in spite of a submarine ridge (with, however, 700 fathoms of water over its greatest depression) extending to Saba, there is no evidence of a dry-land connection of the latter

with the rest. He also places some facts on record in regard to an asserted desiccation of the island of Santa Cruz, and concludes that there is no sufficient proof of it nor of an alleged conflagration caused by the French colonists in 1650.

To the "History of Fremont county, Iowa," Professor Call has contributed a chapter on the geology and natural history, which has been separately issued, with new pagination, with the date of Nov., 1880. The Mollusca are treated of on pp. 34-36, where is given a list of thirty fresh-water and ten land shells, none of them peculiar to the locality, more than half of which are bivalves, mostly Naiades.

In the Annals N. Y. Acad. Sci., 11, 1881, pp. 129-139. Dr. Stearns discusses the introduction of Helix aspersa L., in California, together with the synonymy, relations and habitat of several South Californian species.

"On the geographical distribution of certain fresh-water mollusks of North America, and the probable causes of their variation" (Part 1, Jan., 1881, pp. 8; Part 11, July, 1881, pp. 11; Journ. Cincinnati Soc. Nat. Hist, IV, 1881). The two papers above cited contain an interesting resumé, from Professor Wetherby's point of view, of a number of singularities in geographical distribution of American fresh-water shells. We are of the opinion that when the facts are fully determined in regard to the fossil as well as the recent forms, which unfortunately is not yet the case, results of value will be obtained. The author wisely does not, as yet, endeavor to formulate any results, but calls attention to the facts with a promise of further studies in the future.

Stearns (AM. NAT., May 1881, pp. 362-6) discusses the distribution and synonymy of " Mya arenaria in San Francisco bay," arriving at the doubtless correct conclusion that it has been introduced probably not earlier than 1872 or 1873, on oyster "seed," planted by importers from the eastern coast, to grow and fatten in the bay. It has now almost entirely superseded other "clams" in the San Francisco markets, and has spread or been introduced also at Santa Cruz.

Dr. Lockwood notes (AM. NAT., Nov., 1881, p. 908) the finding of the third fresh specimen (since 1876) of Argonauta argo L., on the New Jersey coast. Two occurred at Long Branch, the other fifteen miles south of it. One was living when found. The

argonaut may therefore be said with truth to belong to the fauna of the east coast of the United States.

"Observations on the species of the genus Partula Fér., with a bibliographic catalogue," by W. D. Hartman, M.D. (Bull. Mus. Comp. Zool., IX, No. 5, 8vo, pp. 171-196, with two diagram plates, Nov., 1881).

This paper contains no descriptions of new species, but is a succinct review of the genus in general, with a list of the species with references to descriptions and figures; a list of terrestrial species as distinguished from those which live in trees; another. list of spurious species in which the reference to P. auriculata Pfr., as a Tornatella would seem to be a typographical error. There is also an account of an examination of two bushels of duplicates from the Pease collection now in the possession of the Mus. Comp. Zoology, and two plates of diagrammatic maps prepared by Andrew Garrett, showing the distribution of the forms of Partula on five of the Polynesian islands. It would seem as if a very important contribution to the study of the origin of species might be made by a keen eyed and competent observer who should be willing to devote himself for a year or two to the study of these extremely local races, their environment and hybridization, on one of these islands. It is perhaps unnecessary to say that the information in this paper is fuller and more accurate than is to be elsewhere found on the same topic, and that it will be a welcome contribution should Dr. Hartman complete, as it has been rumored was his intention, a similar annotated synonymical catalogue of the Achatinellida.

Dr. W. D. Hartman has had printed "A Catalogue of the genus Partula" (F. S. Hickman, West Chester, Pa., 1881, 8vo, pp. 14, cuts), enumerating the species with their synonyms, and dividing them into two sections, of which one contains ten and the other five subordinate groups, and these again are subdivided by characters of less importance. To the divisions of the sections new names have been applied, and they are termed subgenera, though the characters by which they are separated are superficial rather than structural. These subgenera are as follows: Partula (P. faba p. 6); Nenia (P. N. auriculata, Brod. p. 7); Astræa (P. A. dentifera, Pfr. p. 7; preoccupied in cœlenterates, 1789); Clytia (P. C. umbilicata, Pse. p. 8; preoccupied in cœlenterates, 1812); Ilia (P. I. lutea, Lesson, p. 8; preoccupied in crustacea, 1817); Enone (P. Œ. hebe, Pfr. p. 9; preoccupied in vermes, 1817); Helena (P. H. Otaheitana, Brug. p. 9); Pasithea (P. P. spadicea, Reeve, p. 10;