1919.] 



NATURAL SCIENCES OF PHILADELPHIA. 



221 



prominence is probably homologous with the peg of ordinary Neritid 

 opercula, and the very shght projection above and connected with 

 it may be the remnant of a rib. At each end there is an impressed 

 scar of attachment. 



Cavech River, Guatemala, at or near high tide, rare: found with 

 Neritina virginea and N. punetulata, the latter in abundance. 

 Collected by A. A. Hinkley. 



The process of the operculum is so much shorter than that of 

 N. succinea that we have possibly a new species; but veiy few 

 have been examined. 



Schasicheila hinkleyi, n. sp. Figs. 9, 10. 



The shell resembles that of S. pan?iucea Morelet except that it is 

 larger. It is thin, between chamois and cream-buff when clean; 

 densely clothed with subequal spiral cuticular threads. The last 

 whorl is indistinctly angular in front. The lip is somewhat ex- 



Fig. 9. — Schasicheila hinkleyi, shell and operculum. 



panded, rather deeply notched above (about as in S. pannucea). 

 The straight inner margin forms a raised ledge. 



Alt. 8.5, diam. 11 mm.; 3f whorls. 



The operculum has a short, obliquely projecting process at the 

 upper, and a long one, parallel to the straight margin, at the lower 

 angle; the concave outer face is papilose. 



Chama, Guatemala, collected by A. A. Hinkley. 



The operculum of S. pannucea, as figm-ed by Fischer and Crosse, 

 has no superior projection, and the lower process is far shorter than 

 in this species. 

 Cyrenoidea guatemalensis n. sp. PI. XI, fig. 9. 



The shell is orbicular, rather plump, whitish under a very pale 

 brown cuticle. Sculpture of very fine concentric striae with thin 

 cuticular edges. It resembles C. floridana Dall except that the 

 hinge plate is shorter and wider anteriorly, and the posterior end 



