274 WEST CUBAN OBELISCUS. 



1. c. Stenogyra d., BLAND, Ann. Lye. Nat. Hist, of N. Y., 

 xi, p. 85 (viviparity). Stenogyra liasta Pfr., BINNEY, Ann. 

 N. Y. Acad. Sci., iii, p. 100, pi. 15, f. i (jaw), pi. 7, f. D 

 (teeth). 



No description or figure of this shell has hitherto been pub- 

 lished, although there have been many references to it in the 

 literature of Antillean snails. The shell differs from the 

 Porto Rican 0. liasta by its simply concave columella and 

 straight internal axis. Its relation to the true 0. domini- 

 censis of Santo Domingo remains to be determined. 



Subgenus LYOBASIS Pilsbry, 1903. 



Lyobasis PILS., Manual of Conchology, xv, p. 175 (April 9, 

 1903), for gonostoma and paradoxa, the former selected as 

 type. Stenogyra, Opeas and Cylindrella of authors. 



The shell is spire-shaped, fusiform or column-shaped, 

 ribbed or rib-striate, two embryonic whorls smooth, large. 

 Whorls 9 to 13, the last normal or becoming free. Aperture 

 piriform or narrowly ovate, very oblique. Axis straight in 

 the earlier, becoming more or less sinuous in the last one or 

 two Whorls. Type 0. gonostoma. 



Distribution: Western Cuba. A very distinct group of 

 diminutive Obelisks, inhabiting an area where no other forms 

 of the genus occur. The shells are chiefly remarkable for 

 their strong sculpture. Some of the species are markedly 

 senile. They are illustrated on plate 33 and the lowest line 

 on plate 31. 



Key to species of Lyobasis. 



a. Last whorl free in front, the peristome continuous. 



b. 12 to 13 mm. long with 13 whorls, the last with a 



median spiral sulcus. 0. paradoxus, no. 31. 



& 1 . 12 to 13 mm. long with 10 whorls, the lasit not mes- 



ially sulcate. 0. gonostoma, no. 32. 



a 1 . Last whorl in contact, but with a continuous peristome 



in the adult stage; spire thick; rimate. 



b. 14 to 15 x 3 rum., aperture 3 mm. ; whorls 9i/> to 10. 



0. microstoma, no. 33. 



