MUSEUM OF COMPARATIVE ZOOLOGY. 77 



Leucosyrinx subgrundifera Dall. 



Plate XXXVIII. Fig. 1. 



Pleurotoma subgrundifera Dall, in Agassiz, Three Cruises of the Blake, II. p. 66, fig. 

 283, 1888. 



Shell fusiform with an acute spire, nine whorls, and a globular brownish, 

 shining, smooth nucleus of about two whorls ; shell with a polished surface 

 over a straw-colored very thin outer layer, the only transverse sculpture being 

 due to the faint incremental lines and irregularities of growth ; spiral sculp- 

 ture of an extremely sharp and wide keel nearer to the suture in front than to 

 the one behind, and in some cases having its edge actually curved forward and 

 overhanging ; the margin of the keel is smooth and a little rounded ; it is 

 fainter on the last whorl of the adult ; in front of the keel on the base is a 

 slight angulation or hardly elevated thread on which the suture coils ; in front 

 of this are some faint spiral markings, hardly breaking the smoothness of the 

 surface ; suture distinct ; aperture narrow ; notch deep, wide, extending from 

 the suture nearly to the edge of the keel ; outer lip thin, arched forward, not 

 internally lirate ; pillar lip slightly excavated, white, smooth ; pillar straight, 

 attenuated in front, canal narrow, straight, shallow; base moderately rounded 

 in the adult, flatfish in the young ; operculum as in L. tenoceras. Lon. of 

 shell, 30.0 ; of last whorl, 20.3; of aperture, 17.0; max. lat. of shell, 11.0 mm. 



Habitat. Yucatan Strait, a fragment in 640 fms. U. S. Fish Commission 

 Station 2384, Gulf of Mexico, in 940 fms., mud, between the delta of the Mis- 

 sissippi and Cedar Keys, Florida ; and Station 2628, in 528 fms., sand, 100 

 miles S. E. by S. from Cape Fear, North Carolina; temperatures 38°. 7 and 

 39°.6 F. 



Some specimens of this singular shell look like a lot of successively smaller 

 umbrellas, one over another. 



None of the Challenger species approach this one. The Surcula staminea 

 and S. gonioides of Watson are carinated, but the keel is far less pronounced 

 than in the present species, and they do not appear to have that curious chalky 

 outer layer like a coat of whitewash varnished, which is so peculiar in L. sub- 

 grundifera. In the last there is some variation in the strength of the basal 

 spirals, but in none of them do the latter rise much above the surface. 



Subgenus ANCISTROSYRINX Dall. 



Ancistrosyrinx Dall, Bull. M. C. Z., IX p. 53, Aug. 12, 1881. 

 Candelabrum Dall, 1878, non Blainville, 1830. 

 ? Columbarium sp. Tryon, non Von Martens. 



This very elegant section of the family extends from the Eocene, where it 

 has been found at Jackson, Mississippi, and probably in Europe, to the exist- 

 ing fauna. The only species which may perhaps be referred to it that was 

 known before the writer called attention to it is Pleurotoma cedonulli Reeve, 



