1922] NATURAL SCIENCES OF PHILADELPHIA. 61 



E. microdina microdina (Morelet) (1851). Vera Paz, Guatemala. 



E. microdina chryseis (Tristram) (1861). Guatemala (may be a sex-form). 



E. simpsoni Ancey (1886). Utilla Island, Bay of Honduras. 48 



Of this subgenus, I have only been able to examine E. rupestris 

 (Pfr.) (1839) 49 , but this species agrees quite well in shell characters 

 with the typical, mainland species. The A-central has no definite 

 cusps, altho its margin is slightly wavy. The B-central has three 

 rather irregular cusps. The C-central has 2 or 3 points (Plate 

 VI, fig. 28). The T-lateral has no definite cusps on the margin, 

 but the horny thickenings of the umbrella-shaped cutting-edge 

 show four or five irregular, but sharply marked folds, which gives 

 the tooth a wavy appearance under certain lights. A. J. Wagner 

 has described the shell characters of the group, although I doubt 

 the inclusion of some of the larger species. 



Subgenus PRIOTROCHATELSA Fischer. Isle of Pines. 



Prictrochatella Fischer (1893). Type H. constellate Morelet (1847). Isle 

 of Pines. 



In this subgenus, the radulae of E. stellata 50 and E. torrei 51 have 

 been examined. The radular formulae of both are given in Table 

 IV, and that of the former is figured (Plate VI, fig. 30). The 

 radula of this subgenus is practically the same as in Eutrochatetta 

 s. s., except that the R-central is broadly elliptical, instead of 

 circular. A. J. Wagner indicates this as a primitive group, but I 

 regard it as among the most highly specialized forms in the whole 

 subfamily. 



The operculum is superficially something like that of Geotro- 

 chatella, but in Priotrochatella the calcareous plate is dominant, 

 while in the eastern group the horny plate is best-developed. The 

 calcareous portion of the operculum of Priotrochatella is similar 

 in texture to that of Eutrochatella s. s., and is not spiral but practi- 

 cally linear. The nucleus, which is spiral as throughout the family, 

 is quite near the columellar margin, and the growth-lines mainly 

 show externad. I regard it as simply a specialized condition of 

 the Eutrochatella-operculum, due to the shape of the aperture. 



48 In addition, H. exigua Pfr. (1849), from Honduras (Dyson), may possibly 

 belong here, but it is unrecognizable from description. 



49 1 dried specimen; A. N. S. P. no. 15081; collected in Cuba by Poey. 



60 1 dried specimen; A. N. S. P. no. 118935; Sierra de Caballos, 1. of Pines 

 .(W. F. Clapp). 



51 1 dried specimen; A. N. S. P. no. 15083; Isle of Pines (R. Arango). Wm. F. 

 Clapp (1918) has described and figured the radulae of the three species of this 

 genus. 



