68 THE NAUTILUS. 



tralian species' G. petterdi and beddomei. It is nearly allied to 

 Aneylus, from which it differs anatomically by a distinct pattern of 

 radula, and couchologically by its compound shell. The existence, 

 variously affirmed and denied, of a jaw, is now demonstrated by fig- 

 ures. It has been suggested, but not proved, that in unfavorable 

 circumstances the shell never attains its compound development, but 

 remains simple. From an Aneylus of the same size the subcentral 

 nucleus and regular elliptical outline distinguish young Gund- 

 lachia. 



A fuller knowledge of the development and structure of the 

 genus is very desirable. 



The nearest, in phylogenetic array, to Gundlachia are probably 

 the New Zealand Latia and the Tasmanian Ancylastrum. Should 

 Hutton's Latiidce win acceptance, which seems doubtful, it might 

 include these. 



The distribution of Gundlachia agrees in part with that of the 

 recent marsupials, and the theory of a Mesozoic or older Tertiary 

 migration to or from Australia across the south pole, when a lost 

 land with a mild climate united Tierra del Fuego to Tasmania, 

 would explain its present position. 



A NEW MEXICAN BYTHINELLA. 



BY HENRY A. PILSBRY. 



Bythinella palomasensis. 



Shell small, ovate, rapidly tapering above from the periphery of 

 body-whorl to a blunt apex ; composed of four very convex whorls, 

 the last about five-sixths the entire length of the shell, well rounded 

 out. Surface showing faint growth-wrinkles only. Aperture ovate, 

 subangular above, its longest axis about half the length of the shell ; 

 peristnme thin, continuous across the parietal wall and nearly 

 straight there, although not appressed to the body-whorl. Umbili- 

 cus minutely perforated. Color whitish corneous and somewhat 

 translucent. 



Alt, 2'75, max. diam. 1'80 mm. Longer axis of aperture r.SH mm. 



Two specimens from Lake Palomas, northeastern Mexico, col- 

 lected by Dr. E. A. Mearns, U.S. A., of the International Boundary 

 Commission. One of the two specimens has the latter third of a 



