258 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



BoRSONiA Bellardi, 1S38. Shell fusiform, with spiral and axial sculpture, the 

 anal sulcus close to the suture, wide and shallow ; the canal elongated, the pillar 

 with a single plait (or, according to Cossmann, in the type species two) on the 

 proximal part of the pillar. Type B. prima Bellardi. 



The abyssal and Pacific Coast species are sufficiently different and numerous to 

 stand as a distinct group from that containing the Italian fossils, as follows : 



BoRSONELLA Dall, nov., 1908. Shell with a small, blunt nucleus of one or 

 two whorls, sculpture chiefly spiral, feeble, except for one or two spiral carinae, 

 sometimes with a few small riblets or beads on the principal carina; periostracum 

 conspicuous, smooth or vermiculate ; canal wide and very short; outer lip sharp, 

 simple, arcuate; pillar soHd, with one strong, nearly horizontal plait continuous 

 upon the whole axis; axis impervious, opei-culum absent. Type Borsonia dalli 

 Arnold. 



There is never more than one plait in Borsouella ; iu Cordieria, as restricted by 

 Cossmann, there are never less than two. In Rouaultia the anal sulcus is narrow, 

 sharp, and situated at the shoulder iu the peripheral carina. Both Cordieria and 

 typical Borsonia have a long and slender canal and the general aspect of Gera- 

 mula, while Borsouella resembles an Autiplanes with a strong plait on the 

 proximal part of the pillar. 



Gymnobela Verrill, IBSl. Shell ample, stout, smaller than the average 

 Pleurotomella, with a short spire and no operculum. Type G. curta Verrill. 



These shells occupy, so far as the shell characters are concerned, a place in the 

 Mangiliinae analogous to that which is assigned to Bela among the operculate 

 forms. 



Pletjkotomella Verrill, 1873. Shell with a small blunt nucleus of several 

 whorls, closely arcuately axially ribbed, the succeeding whorls with axial and 

 spiral sculpture, short-fusiform ; the anal sulcus close to the suture, deep and 

 ■wide, with a distinct fasciole ; canal very short, narrow, recurved ; outer lip thin, 

 simple, sharp ; pillar thin, gyrate, anteriorly obliquely truncate, almost pervious. 

 Animal blind, iiioperculate. Type F. packardii Verrill. 



The original type was a small, very delicate shell, but species subsequently 

 added to the group attain a notable size and solidity. 



Phtmorhtnciics Dall, 1908, nov. Shell thin, smooth, or spirally sculptured, 

 axial sculpture less conspicuous; fusiform, canal nearly obsolete, ])illar and outer 

 lip simple ; sulcus wide, shallow, close to the suture ; animal blind, with a dis- 

 tinct muzzle into which the proboscis is retracted, operculum wanting. Type 

 Pleurotomella castanea Dall. 



The average I'leurotomoid gastropod, as far as indicated by the animals figured 

 and those examined by the writer, has a simple orifice under and covered by the 

 head and expanded tentacular bases; in the species of the present section a pro- 

 jecting flat-ended muzzle exists, which permanently extends beyond the line 

 joining the tentacles, and into an aperture iu the cud of which the proboscis is 



