1921] NATURAL SCIENCES OF PHILADELPHIA. 375 



Bittium yaquense (Gabb) Plate XXXV, fig. 12. 



Cerithium yaquensis Gabb, Trans Amer. Philos. Soc, xv, 1873, p. 238. 



There are about two varices on a whorl. On the sph-e there are 

 vertical rounded ribs between the varices, but these disappear on 

 the last one or two whorls. The whole shell is spirally striate. In- 

 side there are short spiral lirae within the varices. 



Length 10, diam. 3.8 mm.; 9 whorls remaining. 



Length 9, diam. 3.1 mm.; 11 whorls. 



Type no. 2619 A. N. S. P. 



The type figure is from a shell not quite mature. Most of the 

 specimens are either immature or somewhat broken. 



Bittium asperoides Gabb. Plate XXXV. fig. 4, 



Bittium asperoides Gabb, Trans. Amer. Philos. Soc, xv. 1873, p. 239. 



There are four spiral threads on each whorl, with another visible 

 in the suture, and on the last two whorls traces of one or two faint 

 ones between the major threads. Base with six equal spiral threads. 

 On the penult whorl there are 15 axial ribs, counting the two varices. 



Length 4.1, di?m. 1.4 mm.; aperture 0.85 mm.; 11 whorls. 



Type no. 2616 A. N. S. P. It is an abundant species. 



In a fofm which we take to be a variety (var. asperandum) there 

 are more spiral threads, 8 between sutures, and slenderer, more num- 

 erous and more arcuate ribs, about 19 on the penult whorl. Length 

 2.8, diam. 0.95, aperture 7 mm.; 11 whorls. 



Type no. 3100 A. N. S. P. 



Alabina canaliculata (Gabb) Plate XXXV, fig. 2. 



Bittium canaliculatum Gabb, Trans. Amer. Philos. Soc, xv, 1873, p. 239. 



Shell imperforate, rather thin, turrited. The sculpture consists 

 of even, rounded, backwardly arched ribs which scarcely pass over 

 the periphery of the last whorl, the base being sculptured with about 

 seven spiral cords, the lower ones very weak. The suture is very 

 deeply impressed, the channel mentioned by Gabb being extremely 

 narrow. In the type specimen there is a low varix at the beginning 

 of the last whorl. Columellar margin reflected above. 



Length 3.3, diam. 1.25 mm.; aperture 0.85 mm.; 10 whorls. 



Length 4.6, diam. 1.6 mm.; 10^ whorls. (Type). 



Type no. 2618 A. N. S. P. 



Bittium (Styliferina) cerithidoides Dall, differs from this species 

 by its carinate upper whorls. 



In some of the specimens one or two weak spiral cords may be 



