EASTERN PROVINCE SOUTHERN REGION SPECIES. 357 



with 8 laterals. The sixteenth marginal tooth is shown. A specimen 

 from west coast of Florida (H. nemphill) had lG-1-16 teeth, 7 on 

 either side being laterals, all like what I have lignred in Terr. Moll., 

 V, for those of 31. incrnstaia. Fig, 385 a. 



HEMITROCHtJS, Swainson. 



Animal heliciform (of H. varians), stont, anteriorly blunt, posteriorly 

 long, acutely- terminating; mantle central, 



Fig. 386. 



thin, simple, protected by a shell ; no dis- 

 tinct locomotive disk ; no caudal mucus 

 pore ; respiratory and anal orifices snbcen- 

 tral, on the right side of the mantle, under 

 the peristome of the sliell, generative ori- Animal oi h. varians. 



fice not observed, probably behind the right eye-peduncle. 



Shell external, with the perforation open or closed, globose, shining; 

 spire short; whorls 4-5, the last large, deflexed at the aperture; colu- 

 mella dilated at the base ; aperture contracted, subvertical, roundly 

 lunate; peristome simple, obtuse, labiate within, its margins distant. 



A West Indian genus; one species has been introduced into the 

 Florida Subregion. • 



In Ann. Lye. iST. H. of IS". Y., X, 341, I have, in connection with my 

 friend Mr. Bland, shown the necessity of using this name in preference 

 to Folymita. I will here simply repeat that the type of the latter 

 genus is muscarum, Lea, from which the other species formerly associ- 

 ated with it differ generically in dentition. They will therefore be 

 known bj" the first published name, Hemitrochus. 



The jaw is strongly arched, with acuminated ends, smooth anterior 



Fig. 387. surface, and decided median prominence to cutting margin. 

 Fig. 387 represents the jaw of rarians. The other West 

 Indian species examined by me have the same type of jaw, 

 excepting H. 31illeri, which has one short median rib. 



The lingual membrane (Terr. Moll., V, Plate IV, Fig. L) 

 has about 32-1-32 teeth ; another specimen gave 43-1-43 teeth, with 17 

 perfect laterals. The central tooth has a long, narrow base of attach- 

 ment, with lower, outer, angular expansions and fig.sss. 

 incurved lower margin. The reflected portion is ^^ ^^^^.^-^ c^ 

 only about one-half the length of the base of at- ^3 ^Hj j\}Q 

 tachment, is short, and bears one short, stout '^ js ^^ 

 cusp, with an equally short, stout cutting point; Lingual dentition of 

 the side cusps and cutting points are obsolete. ii.varians. 



