MUSEUM OF COMPARATIVE ZOOLOGY. 83 



Florida, and westward to Cape Catoche, Yucatan, U. S. Fish Commission, and 

 other authorities. 



The deep-water specimens of this species are all dead, and I believe them to 

 be adventitious. 



Drillia Tryonii n. s. 



Shell recalling D. ostrearum, but white, more acutely pointed, smaller, with 

 a more gibbous varix in the adult, an umbilical chink on the pillar, and a 

 spirally threaded fasciole instead of a smooth one; shell eight- whorled, with a 

 smooth nucleus; 16-18 long transverse ribs extending across the whorls, fas- 

 ciole and all; crossed by numerous (eleven on the last whorl but one) ele- 

 vated, even, rounded threads, with about equal or wider interspaces ; the 

 threads are not swollen at the intersections ; suture distinct, the fasciole but 

 slightly excavated, whorls moderately rounded ; on the last whorl, a quarter 

 of a turn before the adult aperture is formed, is a prominent swollen rounded 

 varix, or rib ; aperture short ; body callous ; pillar reflected, forming a distinct 

 pseudo-umbilicus; outer lip thin, not lirate, strongly arched; canal short, 

 curved. Lon. of shell, 12.0; of last whorl, 7.0; of aperture, 5.2 ; max. lat. of 

 shell, 4.3 mm. 



Habitat. Station 231, near St. Vincent, in 95 fms.; Station 262, near Gre- 

 nada, in 92 fms.; Station 272, near Barbados, in 76-100 fms. 



I regard this as a shallow-water species, adventitious in the above localities. 

 All the specimens are injured, but from the lot a description was practicable. 

 These shells, by some error of observation, were returned to me as a variety of 

 D. ostrearum by Mr. Tryon. They are a well marked and perfectly distinct 

 form, having only the most general resemblance to D. ostrearum. The average 

 dimensions of the latter, from the same region, are, lon. of shell, 17.0 ; of last 

 whorl, 10.0 ; of aperture, 7.5 ; max. lat. of shell, 7.0 mm. 



The nearest relative among the Blake shells to this form is D. albicoma, from 

 which D. Tryoni will be distinguished by its smaller size, its more numerous 

 and close-set ribs, and by its strongly differentiated fasciole. 



Drillia albicoma n. s. 



Plate X. Fig. 8. 



Shell solid, slender, acute, pure white, with a simple polished nucleus of a 

 whorl and a half, followed by nine normal whorls ; spiral sculpture of ex- 

 tremely fine, close-set, regular threads, uniform over the entire surface, but 

 scarcely visibly developed in the first four whorls, which appear polished to 

 the naked eye ; the threads on the last whorl are about nine in the breadth ol 

 a millimeter; transverse sculpture of rather stout, sharp ribs (on the seventh 

 whorl ten) which extend from suture to suture, with a slight fiexuosity near 

 the suture, but no marked interruption for a fasciole ; on the last whorl there 

 are fourteen of these ribs, beside the large shouldered varix behind the aper- 



