THE CYCLOPHORTD LAJSTD MOLLUSKS OF AME.RTCA 109 



At first glance one might consider this to be Aperostoma {Gycla- 

 damsia) seminudum (C. B. Adams), as far as the general shape and 

 color scheme are concerned, but it can at once be distinguished by 

 its poterid operculum. 



POTERIA (POTERIA) LINEATA (Gray) 



Shell varying from helicoid to decidedly elevated helicoid in out- 

 line, unicolor or banded ; periostracum ranging from brownish buff 

 to chestnut colored. The nucleus consists of 1.5 decidedly elevated, 

 mflated, strongly rounded, smooth whorls. The first 2 postnuclear 

 whorls are marked by slender, very regular, retractively curved axial 

 riblets ; beyond this the axial riblets become less regular and on the 

 last whorl are mere elevated incremental lines. On the last whorl 

 wrinkles make their appearance on the upper surface; they are of 

 irregular size and irregularly disposed. Here, too, spiral threads 

 are present. The suture of the early whorls is well impressed; on 

 the last two the summit of the whorls is appressed to the preceding 

 turn, and the suture becomes less conspicuous. Periphery well 

 rounded. Base well rounded, openly umbilicated, with a strong keel 

 marking the outer edge of the umbilicus. The base, also, is marked by 

 irregular wrinkles, but here they assume a more spiral arrangement. 

 The deepest pits are next to the umbilical keel. The umbilical wall 

 is marked by low rounded axial ribs, which, as well as their inter- 

 spaces, are crossed by incremental lines. Aperture subcircular, 

 oblique, decidedly protracted into an angulation at the posterior 

 angle; the outer lip of the peristome is thin, the inner, thickened, 

 particularly so at the umbilical keel. Operculum typically poterid. 



I am recognizing two subspecies, which the following key and 

 descriptions will help to differentiate : 



KEY TO THE SUBSPECIES OF POTERIA (POTERIA) LINEATA 



Height more than 20 mm lineata 



Height less than 17 mm cycloata 



POTERIA (POTERIA) LINEATA LINEATA (Gray) 



Plate 16, FioxmEs 34-36 ; Plate 42, Figures 14, 15 



1843. Cyclostoma jamaicense Sowekby, Thesaurus conchyliorum, vol. 1, p. 96, 

 No. 15, pi. 23, fig. 12 (not Cyclostoma jamaicense Gray, 1828). 



1850. Cyclotus (Poteria) Imeatus Gray, Nomenclature of the molluscous animals 

 and shells in the collection of the British Museum, pt. 1, Cyclophoridae, 

 p. 11. 



This subspecies appears to be the most abundant race in Jamaica. 

 It is rather widely distributed. We have specimens from Westmore- 

 land, St. James, St. Elizabeth, Manchester, St. Ann, and Clarendon 



428349 — 42 8 



