194 



protoconch its previous site is closed by a sunken lamina with 

 subdistant erect transverse lamellae, convex posteriorly. Be- 

 tween it and the anterior margin is a differentiated rib, 

 broader and higher than the rest, fissured superficially 

 throughout. In its upper part the fissure is as wide as the 

 perforation, but is nearly closed internally by horizontal 

 laminse from the sides. It gradually contracts anteriorly 

 to a fine line; in its upper half the fissure communicates with 

 the interior, in the lower it is shut off. The slit fasciol© and 

 perforation are bounded on each side by a delicate erect lam- 

 ina, highest at the perforation, in front of which the laminae 

 gradually approximate to form the differentiated rib. From 

 the protoconch to the margin this lies a little to the right of 

 the actual median line of the shell. Sculpture : Radial ribs, 

 well rounded, nearly smooth, about as wide as their inter- 

 spaces, sixteen primary, but increasing rapidly by intercala- 

 tion of secondary and tertiary riblets to 90 in a shell of 10 

 mm. length, and crenulating the margin. These riblets ap- 

 pear first as gradually enlarging tubercles in the centre of 

 the intercostal spaces, situated on the concentric laminae, 

 which conspicuously cross the interspaces, slightly scale the 

 bases of the ribs, but are barely visible under the microscope 

 on their summits. They produce radial lines of punctations 

 in the interspaces, and in old dead specimens, where the glaze 

 disappears from the interior, these appear as perforations. 

 The ribs posteriorly are broader and closer together. Inter- 

 nally a small shelf or septum convex towards the interior, with 

 a sharp simple margin anteriorly hides the upper fourth of 

 the perforation, being attached to the shell at a distance from 

 the margins of the perforation about equal to the width of 

 the perforation; it gets gradually narrower and less obvious 

 posteriorly. Its dorsal surface slopes up to the slit fasciole, 

 the last one or two scales of which roof in the back of its 

 cavity. From the perforation anteriorly runs a gutter to 

 the margin; in older examples this becomes a thin central 

 ridge. Shallow radial furrows correspond with the external 

 ribs. As individuals get older, the shell grows more rapidly 

 posteriorly, so that the apex gets less eccentric, and the back 

 part becomes very flat and sloping. 



Dim. — When half-grown, length, 10 mm.; width, 8 mm. j 

 height, r4 mm. ; apex, 1*8 mm. from the posterior end. When 

 full-grown, length, 18 mm.; width, 15'4 mm.; height, 4*7 mm.; 

 apex, 5'4 mm. from the posterior end. 



Locality.~l30 fathoms, off Cape Jaffa, 20 whole or 

 broken; 300 fathoms, 4, all dead. 



Obs. — The shell appears to fall within the limits of 

 Cranopsis. I have no shells of this genus with which to com- 



