MUSEUM OF COMPARATIVE ZOOLOGY. 127 



George'3 Bank, off Nantucket Shoals, off Maryland, and off Hatteras, North 

 Carolina, in 100 to 1608 fins. 



In the typical form the transverse riblets are sharp-edged, the spirals are 

 faint or tend to become so, the spire is low, and there is a tendency to corona- 

 tion or the formation of a wrinkled band in front of the suture. When perfect, 

 the notch is cmite shallow, as in Bela. The epidermis is pale, glistening, and 

 Bmooth. 



Pleurotomella (Gymnobela) Blakeana var. agria Dall. 



Shell in general resembling P. Blakeana, but differing by more elevated 

 6pire, by the much stronger closely set spiral threads, which cover the whole 

 shell, by the rounder and more oblique riblets confined to the vicinity of the 

 angulation in the adult and nearly absent on the spire, and the columella so 

 arched and twisted as to make the axis nearly pervious. The epidermis is 

 rougher and darker than in the type and there are six whorls without the nu- 

 cleus. Lon. of shell, 10.0 ; of last whorl, 7.5 ; lat. of shell, 6.0 mm. 



Habitat. U. S. Fish Commission Station 2723, 125 miles off the mouth of 

 Chesapeake Bay, in 1685 fms., gray ooze. 



The typical form and a specimen of this well-marked variety were collected 

 together. 



A much larger shell with the surface much eroded was collected by the 

 Blake at Station 173, in 734 fms., near Guadelupe. In this the general form 

 has become more oval, the angulation a sharp keel forming a notch in the 

 outer lip, and when perfect probably marked with vaulted scale-like projec- 

 tions. There is a sulcus in front of this keel. The slope from the suture to 

 the keel is much steeper than in var. agria, and even a little rounded. Before 

 the sulcus the whorl is covered with coarse primary threads, over and among 

 which are a finer secondary series. The columella is callous and twisted, there 

 is a short but evident canal, slightly recurved, and followed by a siphonal fasci- 

 ole. The transverse riblets appear to have been well marked only on the 

 periphery. There are five whorls, but the apex is eroded ; there were perhaps 

 two and a half more beside the nucleus. I regard this as probably the adult 

 form of the var. agria, but it is too imperfect to decide with certainty. 



Pleurotomella (Gymnobela?) tornata Verrill 

 var. Malmii Dall. 



Taranis Morchii Dall, Bull., M. C. Z., IX. p. 70, 1881 ; Verrill, Trans. Conn. Acad., 

 V. pp. 486, 487, 1882 ; not of Jeffreys. 



Habitat, Station 2, in 805 fms. 



This is the form with subspinose sculpture. The variety with the spiral 

 sculpture strongest is the variety tomatus Verrill (op. cit., VI. p. 251, 1884), 



