184 CURRENT LITERATURE. 



Mead, A. D. — Observations on the soft-shell clam. 30th Ann. Rpt. Commis. 

 Inland Fisheries, U.S,A., 1900, pp. i — 25, pis. i — xi. 



The author here gives some interesting details relating to the life history, &c. of 

 the soft-shell clam. The eggs are exceedingly minute and the egg-laying period 

 probably extends over .May and June. They are extruded in large numbers, and 

 in a short time after fertilisation, deveiope into minute free swimming forms not at all 

 like the adults. In this condition they live for several days and are carried away 

 by the tides, they then settle down and attach themselves to some object, a stone or 

 a piece of sea-weed. The experiments of transplanting seem to prove that the rate 

 of growth is more rapid than is usually supposed, the most rapid growth taking 

 place where the molluscs are under the water most of the time. Certain facts 

 strongly indicate that they breed during the first year of their life, although the age 

 at which they reach sexual maturity has not been definitely ascertained. 



Pilsbry, Henpy A. — Mdostracon, a new slug-like genus of dart-bearing 

 Hclicidae. Proc. Malac. Soc. Lend., 1900, vol. iv, pp. 24 — 30, jil. ili. 



In this interesting paper Dr. Pilsbry describes a slug-like mollusc derived from 

 the true '' HclLv' stock, to which the name Metostracon mima, n. g. et sp. is given. 



From the anatomical features a relationship to Xanthony.i' is unmistakably 

 indicated. Upon the affinities of these two genera the author makes some valuable 

 observations. At first sight these genera recall the external form of certain 

 Arionidac — Binncya and Hemphillio, the resemblance, however, is only superficial. 

 The Limncidac and Philomycidac are obviously very different, whilst the slug-like 

 genera of the BulimaUdac are clearly bulimuline. It would seem therefore that 

 no known group of slugs will receive Mdostracon and XanUionyx ; but a group of 

 the Hclicidae known as the Iklogona Euadenia, agrees in all the important 

 characters. The nearest allies then are apparently the genera Epiphragmovlwra 

 and Ccpolis, the four genera practically agreeing in all the important anatomical 

 characters, excepting those correlated with the degeneration of the shell. 



Whether Xanthonyx has an ally in the genus Cryptoslracon, W. G. Binn., at 

 present remains doubtful ; this latter genus, the author thinks, may be a more 

 advanced member of a sub-family which would contain the former genus and the 

 new one here described. Seeing that it is by no means certain that these three 

 genera have arisen from the same genus of Helicoid Belogona, the author refrains 

 from so grouping them ; certain anatomical features suggesting parallelism rather 

 than a common phylogeny. This latter view, will, we think, be endorsed by 

 malacologists. — W. E. C. 



Pilsbry, Henry A. — Note on the Anatomy of the Helicoid genus Ashmunclla. 

 Proc. Acad. Nat. Sci. Phila., 1900, pp. 107 — 109, figs, i — 3. 



An examination of the generative organs of A. thomsoniana, Anc, A. porlcrae, 

 Pils. and Ckll., and A. JiyporJiyssa, CklL, fully confirms the anatomical characters 

 ascribed to this genus by the author in 1899. It is very distinct from Polyyyra, and 

 possibly related to the New Mexican species referred to the genus Epiphraymoiihora, 

 which Dr. Pilsbry has examined. ludging from an immature example of E. 

 Jiachitana, he thinks, a series of forms strikingly divergent in the reproductive 

 organs from the Californian forms may be found here. 



Pilsbry, Henry A. — Notices of new Japanese Land snails. Proc. Acad. Nat. 

 iSci. Phila., 19CX), pp. 381 — 384. 



A Key to the Japanese species of Alycaeus is given and the following new 

 species and varieties described : Diplominatina jmsUla v. oyiiiensis, Macroclilamys 

 micrograpta, Kaliella midtivolvis, Vitrea Jmrimensis, Georissa jaiJonica. 



Pilsbry, Henry A.— New South American Land snails. Proc. Acad. Nat. Sci. 

 Phila., 1900, pp. 385 — 394, pis. xi, xii. 



The following are new : Happia ihcringi, Polygyraticc sargenti, P. affinis, P. 



