126 CURRENT LITERATURE. 



shell is to be regarded as a secondary phenomenon. The author therefore concludes 

 that Trstacclla arose from a mollusc similar to Parijphanta, and that in any division 

 of the Agnatha the genus I'anjiilitiitla must come before TcstaccUa. 



BoUVier, E. L. et Fischer, H.— Observations nouvelles sur I'organisation des 

 I'k'urolomiuies. Comjit. Rendus, 1901, vol. cxxxii, pp. 583 — 585. 



The authors give a short account of some parts of the internal structure of P. 

 Icyrichi, Ililg. The operculum is very reduced. The gills are symmetrically 

 arranged in a branchial chamber, both are small, the right being a little smaller and 

 shorter than the left. The feeble development of the gills in Flevrotomaria and 

 their localisation in the anterior half of the pallial chamber, in the authors' opinion, 

 completely justifies Biitschli's view that the respiratory organs of the primitive 

 Diotocard are formed by the forward displacement of two gills which originally were 

 situated behind, to the right and left of the rectum. Between the two gills, the 

 roof of the pallial chamber is richly vasculated, and apparently is homologous with 

 the lung o{ Heli,)'. The respiratory process appears to be equally shared by the two 

 sets of organs, and this the authors are of opinion is the primitive condition. 



.\ / 



Vayssiere, A. — Etude comparce des Opistobranches des cotes Fran9aises de 

 Tocean Antlantique et de la Manche avec ceux de nos cotes Mediterraneennes. 

 Bull. Sci. France et Belg., 1901, T. xxxiv, pp. 281 — 315. 



Professor Vayssiere's interesting paper gives a list of the Opisthobranchs found on 

 the Channel and jUlantic Ocean coasts of France, and a comparison with those 

 found on the French Mediterranean coast. The list comprises 126 species. A 

 remarkable difference exists between the two faunas, thus 16 genera of the Ocean 

 are not found in the Mediterranean, while 14 genera of the latter are not found 

 on the Ocean coast. 



Bergh, R. — Beitrag 7.\\x Kenntniss der Gattung Harpa. Zool. Jahrb. (Abth. f. 

 Morph.), 1901, Bd. 14, pp. 609 — 629, T. 47. 



Ur. Bergh 's interesting study on the structure of IL vcntricosa, Lam., //. rosacea, 

 Mts., If. nablium, Mts. , and //. Diinor, Mts., shows that the Harpidae are probably 

 allied to the Olividac, although many points yet remain obscure, while in some 

 features resemblances to molluscs widely separated are indicated. 



Externally we note that the large, flattened foot is incapable of being withdrawn 

 into the shell, and is devoid of an operculum. The tentacles, which proxinially are 

 close together, exhibit towards the proximal end a well-developed, external optic 

 prominence. There is a long respiratory tube. The alimentary system commencing 

 at the mouth, which is a very narrow opening, has a long proboscis ; the gullet is 

 very small, and the intestine short. The salivary glands are well developed and the 

 digestive gland small. The nervous system is characterised by the concentrated 

 ganglia, resembling in this and other features the condition which obtains in the 

 Bucciniditc. The penis is unarmed and the seminal duct either traverses this organ 

 as an open groove, or passes subcutaneously on and thruugh it. The kidney, peri- 

 cardium and other parts are also brielly dealt with. 



BakeP, F. C. — The Molluscan Fauna of the Oencsee River. Amer. Nat., 1901, 

 vol. XXXV, pp. 659 — 664. 



The Genesee River rises in Potter Co., Penn., and flows in a northerly direction 

 for nearly 120 miles, emptying in Lake Ontario, 7 miles north of Rochester, N.Y. 

 At Rochester the river drops to the valley below in three series of falls of considerab'e 

 magnitude. A study of the Mollusca of the river leads the author to the ft)llowing 

 conclusions: that a series of falls like these prove an effective barrier to the distri- 

 bution of some molluscs, such as pclecypods with mud -burrowing habits and the 

 ctenobranchs, which cling to the rocks and do not come to the surface, while to the 

 freshwater pulmonates, which frequently come to the surfiice and can be swept over 

 the falls, it is not a barrier. A table showing the comparative distribution of the 

 various species accompanies the pajier. 



