1911.] 



NATURAL SCIENCES OF PHILADELPHIA. 



357 



Length of figured specimen 42.5, width 31.6, height 23.2 mm. A 

 larger fragment has an outer lip about 55 mm. long. 



CERITHIID^J. 

 Bittium nugatorium n. sp. Fig. 1. 



The shell is slender, diameter about one-third the length. Embry- 

 onic shell conic, of 3^ smooth convex whorls. Sub- 

 sequent whorls about 6+, convex, with well-impressed 

 suture ; they have three narrow spiral cords, increas- 

 ing to four on the last two whorls, by the addition 

 of a subsutural thread. These are intersected by 

 narrow, slightly nexuous longitudinal ribs, forming 

 a lattice work enclosing square pits. On the last 

 whorl five spirals form this lattice; and there are 

 five smooth spirals without longitudinal ribs on the 

 base. There is a rounded varix on the last whorl. 

 Aperture not perfect. There is a slight anterior 

 channel. 



Length 3.6, diam. 1.2 mm. 



This species is similar to Cerithium collinsii Gabb, 

 from Limon, Costa Rica, in form, but differs by 

 having more embryonic whorls, and three spirals on the whorls of the 

 spire ; moreover, the base has five strong spiral cords. 



Fig. 1. 



TURRITELLID^l. 

 Turritella mimetes n. sp. PI. XXVII, fig. 1. 



The shell resembles T. variegata L. in contour, except that the base 

 is flat and the periphery much more strongly angular. Whorls 14 + , 

 flat, the lower edge of each projecting a little. In the upper third of 

 the shell, each whorl has 16 fine, even threads, equal, and about equal 

 to their intervals. A submedian thread then becomes larger, and on 

 the later whorls there are many unequal spirals of three or four 

 sizes. The flat base has similar spirals, four or five threads being- 

 larger than the other striae. 



Length 64, diam. 18 mm. 



This species differs from the recent T. variegata by the even and finer 

 striation of the upper whorls, the flat base and strongly angular 

 periphery. It is probably ancestral to the modern species. Some 

 fragments indicate that it reaches a larger size than the nearly perfect 

 type specimen. 



