360 PROCEEDINGS OF THE ACADEMY OF [PaRT II 



strida might perhaps be expressed best by a trinomial name, D. 

 constricta crassidens. 



Bursa bufoniopsis Maury. 



Bursa amphitrites Maury. 



See: Bull. Amer. Pal. v, pp. 108, 109. 



Tritonium commutatum Dkr., Gabb, Tr. Amer. Philos. Soc. xv, 1873, p. 211. 



These two forms of the B. affinis group were not differentiated 

 in the Gabb collection, though both are present. 



Bursa crassa proavus n. sutasp. Plate XXIX, figs. 4, 5. 



Bursa crassa Desh., Gabb., Tr. Am. Philos. Soc. xv, p. 212. 



The shell differs from B. crassa (Dillw.) by the broader form and 

 more strongly developed granulation ; the anal sinus is more obHque and 

 shorter, its end is not so high as the summit of the varix behind it. 

 The smooth embryonic shell is Naticoid, while that of B. crassa has 

 a more elevated and conic spire. 



Length 25, diam. 19 mm.; 3^ embryonic and 3| later whorls. 



Type no. 3227 A. N. S. P. 



The Bowden form of B. crassa"-^ is that which approaches the 

 present form most closely, having similar coarse granulation; but 

 it differs by the more conic embryonic stage, and at all stages of 

 growth the anal canal is longer and more direct. It may be called 

 Bursa crassa bowdenensisn.subsp., PI. XXIX, fig. 8. Type no. 3747 

 A. N. S. P. 



In the recent form the granulation is perceptibly finer, or often 

 subobsolete on the last whorl, and another character has come in; 

 in the most progressive examples the peripheral tubercles disappear 

 and one or two intervariceal nodules take their place. 



CASSIDIDAE. 



Cassis sulcifera Sowerby. 



Cassis sulcifera Sowb., Quart. Journ. Geol. Soc. vi, 47, pi. 10, fig. 7, 1849. 

 Gabb, Trans. Amer. Phil. Soc, xv, 222. 



An ancestral form of C. tuberosa L., from which it differs chiefly 

 by the smaller size and the stronger axial riblets, which almost 

 disappear, however, in the largest adults. Sowerby 's figure was 

 from a young specimen. Old ones become triangular, in an apical 

 view, by the predominance of a dorsal tubercle. The largest ex- 

 ample measures: 



Length 90, diam. 80 mm. 



2' Ranella crassa Dillw., Guppy, Q. J. Geol. Soc, xxii, p. 288, pi. 18, fig. 9. 



