MUSEUM OF COMPARATIVE ZOOLOGY. 125 



the canal, where the threads become nearly uniformly coarse. Whorls pre- 

 cedinj,' the last cxtcndiii}^ in a nearly .strai;,Mit line from the keel to the suture 

 before and behind, the incremental lines distinct but not coarse; suture simple, 

 not appresscd ; base neatly rounded, canal moderately long and wide ; sinua 

 rather deep, outer lip arched forward, thin, sharp; inner lip with a thin layer 

 of white callus; pillar and canal nearly straight. Max. Ion. of shell, 20.25; 

 of last whorl, 13.25 ; max. hit. of shell, SJ.O mm. 



Habitat. Station 117, off Porto Rico, northward, in lat. 17° 47' N. and 

 Ion. 67° 3' W., in 874 fms., gritty ooze, bottom temperature 40^. Station 291, 

 near Barbados, in 200 fms., stony bottom, temperature 50°.() F. 



This shell recalls Siircula gonioides Watson, but is more compact, with a 

 proportionally shorter last whorl and canal ; the young of Pleurotomella Ed- 

 gariana Dall has fewer whorls in the same length ; Typhlomangelia Tannery 

 which has a good deal the same general form, is ribbed, has the fasciole more 

 excavated, and the keel or shoulder behind the periphery. In fact, I have not 

 been able to find anything which closely resembles it among figured species, 

 and its nearest relative seems to be the next species. 



? Pleurotomella hadria n. s. 



Shell resembling the preceding in its general features, but larger and stouter, 

 and differing in details of sculpture, etc. It is best described by comparing 

 it with the P. catasarca. The nucleus is similar and there are seven subse- 

 quent whorls ; the keel is less prominent, there is a narrow shallow groove 

 behind it, and then two sharp threads marginating the fasciole, which are more 

 distinct on the earlier whorls ; the spiral threads on the fasciole are crossed, 

 as in P. catasarca, by fine arched ripples, but in P. hadria these ripples are 

 more numerous, finer and closer together, they follow the incremental lines, 

 and, as the sinus is less profound in P. hadria, they are less deeply concave; 

 one of the most marked differences is a series of small oblique riblets, which 

 begin in front of the fasciole or on the keel itself, especially on the earlier 

 whorls, cutting its continuity, and continued obliquely in front of it nearly or 

 quite to the suture as threads reticulating the spirals ; this feature becomes 

 obsolete on the last whorl or half-whorl, and is stronger in archibenthal speci- 

 mens from the Gulf of Mexico than in those from off the Carolina coast ; on 

 the base of P. hadria the threads are hardly divisible into two series, and the 

 alternations of size are very slight, and occur in every other thread if at all, 

 instead of several fine ones intercalated between two primaries ; the aperture, 

 roundness of the base, outer lip, etc., are much as in P. catasarca, but the 

 notch is not so deep, the pillar is not quite so straight, and the canal is a little 

 twisted and plainly somewhat recurved. Max. Ion. of shell (of same number 

 of whorls as the specimen previously described under P. catasarca), 27.0 ; of 

 last whorl, 19.0 ; max. lat. of shell, 13.0 mm. 



Habitat. U. S. Fish Commission Stations 2676, off Cape Fear, N. C, in 

 407 fms., sand, temperature 45°.8 ; 2678, in the same vicinity, in 731 fms., 



