Prof. J. D. Dana on Cephalization. 187 



and Otina, belonging to the Auriculea, with those of Succinea 

 and its allies. From the shell alone, which has the form of Otina, 

 with the substance, texture, and peculiar external ridge and 

 internal furrow of Camptonyoo, I should have supposed the pre- 

 sent species to belong to the last-named genus ; but the retractile 

 eye-bearing peduncles prove its place to be in the neighbourhood 

 of Succinea, from which genus the internal furrow for a siphon 

 distinguishes it as a well-marked subgenus. Tentacles are ex- 

 tremely small and rudimentary in several of the subgenera of 

 Succinea, and, in the present case, appear to be wanting; if 

 present, they are certainly very inconspicuous. The animal of 

 Helisiga, Less., as represented in Adams's Gen. Rec. Moll., 

 'pi. 73, closely resembles that of Lithotis, but has a larger foot, 

 while the shell only differs in the absence of the siphonal furrow. 



Lithotis abounds adhering to the precipitous basaltic rocks 

 of the Western Ghats, like Cremnobates, but apparently in rather 

 more exposed situations, being perhaps more purely an air- 

 breather, and requiring less moisture than its congener. Both 

 probably feed upon the confervoid vegetation covering the sur- 

 face of the rock to which they adhere. 



I am indebted to the kindness of Mr. A. B. Mynne for the 

 accompanying drawings of the shells above described. 



EXPLANATION OF PLATE IV. 



Figs. 1, 2, Cremnobates Syhadrensis, natural size. 



Fiff. 3. The same, enlarged 2 diameters. 



Figs. 4, 5. The same ; operculum enlarged 2 diameters. 



Figs. 6, 7. Animal of the same. 



Figs. 8, 9, 10. Lithotis rupicola, natural size. 



Fig. 11. The same, enlarged 2 diameters. 



Fig. 12. The same; animal from below. 



XIX. — On Cephalization, and on Megasthenes and Microsthenes 

 in Classification {being in continuation of an Article on the 

 Higher Subdivisions in the Classification of Mammals). By 

 James D. Dana*. 



In the paper on the " Classification of Mammals," published by 

 the writer in Silliman's Journal (vol. xxxv. p. 65) f, and also in 

 his earlier paper on Crustaceans, the principle of cephalization 

 is shown to be exhibited among animals in the following 

 ways : — 



1. By a transfer of members from the locomotive to the cephalic 

 series. 



* Communicated by the Author. From the 'American Journal of 

 Science and Arts,' vol. xxxvi. (July 1863). 



t See Ann. and Mag. Nat. Hist. March 1863, p. 207. 



13* 



