22 ORIGIN OF LAND PULMONATA chap, i 



Gasteropoda. — (2) Pulmonata. The origin of these, the 

 bulk of the land fauna, must at present be regarded as a problem 

 not yet finally solved. Some authorities, as we have seen, regard 

 them as derived from the Nudibranchiate, others, probably more 

 correctly, from the Tectibranchiate Opisthobranchs. 



The first known members of the land Pulmonata {Pwpa [?], 

 Hyalinia) are from the Carboniferous of North America. Similar 

 but new forms appear in the Cretaceous, from which time to 

 the present we have an unbroken series. The characteristically 

 modern forms, according to Simroth,^ are Helices with thick 

 shells. According to the same author, Vitrina and Hyalinia 

 are ancestral types, which give origin not only to many modern 

 genera with shells, but to many shell-less genera also, e.g. Testa- 

 cella is probably derived through Daudehardia from Hyalinia.^ 

 while from Vitrina came Limax and Amalia. A consideration 

 of the radulae of the genera concerned certainly tends in favour 

 of these views. 



Godwin- Austen, speaking generally, considers ^ genera of 

 land Pulmonata with strongly developed mantle-lobes and rudi- 

 mentary shell as more advanced in development than genera in 

 which the shell is large and covers all or nearly all the animal. 



1 SB. Naturf. Gesell Leipz. 1886-87, pp. 40-48. 



2 X. and F. W. Moll, of India, iv. p. 167. 



