1921] 



NATURAL SCIENCES OF PHILADELPHIA. 



311 



Retusa biforis Pils. and Johns. Text-flg. 8. 



Proc. A. N. S. Phila. 1917, p. 151. 



Fig. 6. 



Cylichnella bidentata (Orb.) 

 (recent) 



Fig. 7. 

 Cylichnella ovum- 

 lacerti (Guppy). 



Fig. 8. 

 Retusa biforis P. & J. 



Retusa sulcata fossilis n. siibsp. 



Cf. Bulla sulcata Orb., Moll. Cuba i, p. 129, pi. ibis, figs. 9-12. 

 Cylichna sulcata d'Orb. Gabb, Trans. Amer. Philos. Soc. xv, p. 245. 



The fossils agree in sculpture with R. sulcata but they are larger 



and relatively narrower, three of the largest measuring: 



Length 2.8, diam. 1.15 mm. 



Length 2.8 diam. 1.35 mm. 



Length 2.9, diam. 1.25 mm. 



The last two are conspicuously swollen near the base. 



Type no. 3186 A. N. S. P. 



Cylichnella ovumlacerti (Guppy) Text-flg. 7. 



Cylichnella bidentata d'Orb., Gabb, Trans Amer. Philos. Soc. xv, 1873, p. 246; 



Proc. A. X. S. Phila. 1872, p. 273. Not Bulla bidentata d'Orbigny. 

 Tornatina {Cylichnella) ovum-lacerti Guppy, Dall, Proc. U. S. Nat. Mus. 



XVIII, p. 27. 



The Santo Domingan shells are cyHndric-oblong, obtusely rounded 

 below, narrowly truncate at summit ; glossy, encircled by many im- 

 pressed spiral lines in the lower half. The vertex is concave, sur- 

 rounded by a rather sharp keel. Aperture somewhat racket -shaped. 

 Columella having a strong, upper spiral plait which continues to the 

 outer edge of the columellar callus, and a small, subvertical, sig- 

 moid fold below. Outer lip very thick, bevelled to the edge. 



Length 4, diam. 2.4 mm. 



