MUSEUM OF COMPARATIVE ZOOLOGY. 79 



about twenty-six sluiqi short subtricaiigular spines more or less upturned ; half- 

 way between tlie keel and the carina is an elevated second keel, not undulate 

 or dentate but much higher than in A. elegans ; behind this is the sinus, which 

 is indented about one eighth of a turn; the fasciole is concave; transverse 

 sculpture of rather coarse prominent lines ol' growth which are often strongly 

 marked; aperture narrow, elongate, notched for the sinus, the canal, and the 

 carina; canal long, narrow, rather open, slightly curved at the tip; base of 

 shell subconic, hardly rounded, whole surface of the shell having a polished 

 appearance like barley-sugar candy. Lon. of shell, 18.0; of last whorl, 12.5; 

 from the carina to the anterior end of the canal, 10.0; max. lat. of shell, 8.0; of 

 aperture, 3.0 mm. 



Habitat. Yucatan Strait, 640 fms. ; Station 132, in 115 fms., rocky bottom, 

 off Santa Cruz; Station 143, in 150 fms., off Saba Bank; Station 220, in 116 

 fms., rocky bottom, off Santa Lucia; Station 206, in 170 fms., near Martinique, 

 on a bottom of fine sand; Station 273, in 103 fms., coral, off Barbados; Station 

 290 (living), in 73 fms., coral, bottom temperature about 71° F. ; Stations 296, 

 297, and 299, off Barbados, in 84-140 fms., hard or coral bottom. The Fish 

 Commission obtained it in the Gulf of Mexico, between the delta of the Mis- 

 sissippi and Cedar Keys (dead), at Station 2373, in 25 fms., coral; and at Sta- 

 tion 2646 (fresh), in 85 fms., sand, off Cape Florida. 



The soft parts of this species are whitish or pale straw-color. The tentacles 

 are small, the eyes large and black. The operculum, thin and yellow, resem- 

 bles that of Drillia. The sides of the foot are plain, the gills as usual. The 

 single living specimen, very small, was so far retracted that the shell had to be 

 wholly sacrificed to get him out unlacerated. It was a male with a verge of pro- 

 portionally enormous size set on the right side behind the head, smooth, some- 

 what sigmoid, with an oval tip, without any appendix, and slightly flattened. 



This shell was at first confounded with A. elegans, but a comparison shows 

 them to be perfectly distinct, the sculpture being entirely different. The pres- 

 ent species, though not so slender, is more like A. cedonulli, Reeve, than is the 

 A. elegans, the latter in several respects being nearer to the fossil species from 

 the Mississippi Eocene. 



Subgenus GENOTA H. & A. Adams. 

 Genota mitrella Dall. 



Plate XII. Fig. 5. 



Pleurotoma {Genota) mitrella Dall, Bull. M. C. Z., IX. p. 56, Aug. 12, 1881. 

 Pleiirotoma (Genota) didyma Watson, Journ. Linn. Soc, XV. p. 404, Sept. 29, 1881; 

 Chali. Gastr., p. 299, pi. xxii. fig. 5, 1885. 



Habitat. Yucatan Strait, 640 fms.; off Sombrero, in 450 fms., ooze, Chal- 

 lenger Expedition. 



No further specimens of this species have been found. It is referred to 

 Genota on purely conchological grounds. 



