64 SCHISOMOPE. 



whole surface is striated with very fine, slightly raised, distant, very 

 oblique longitudinal threads, and with very similar spiral threads, 

 which are a little finer and closer, but on the upper whorls relatively 

 stronger, these longitudinals and spirals (the latter on the top) cross 

 one another, but not at right angles, and do not form tubercles at their 

 intersections. Spire short, slightly raised. Apex very small, prom- 

 inent; the first whorl and a half seem to be embryonic, and are 

 very finely, microscopically, reticulately scratched. Whorls 4, of 

 not very rapid increase, convex above, rounded at the periphery, 

 and a little excavated on the base by the large-mouthed umbilicus. 

 Mouth large, very oblique, and round, but a considerable section of 

 the circle is cut off by the irregular and twisted pillar. Outer lip 

 descending, well arched all round ; beyond the point of the pillar it 

 sweeps on with a sharp, prominent edge, enclosing the umbilicus, up 

 into which it plunges direct. Inner lip strong and defined, but 

 excessively short and retiring on the body, being cut quite away so 

 as completely to expose the umbilicus, deeply but widely sinuated at 

 the top of the pillar, which is slightly twisted, has an oblique, sharp, 

 rounded, but not at all patulous edge ; is bluntly toothed, and slightly 

 truncate at the point, which does not run out to the edge of the 

 outer lip, but dies out gradually just within it. Puncture consists 

 of a single most minute oval pore, which opens in a slight bulge of 

 the exterior a little way back from the lip-edge, and has a very 

 slightly thickened margin inside ; from it a slight straight furrow runs 

 forwards along the inner surface of the shell ; the surface longitu- 

 dinals bends sharply backwards at the hole, and a little way before 

 the opening is reached, as if preparation were being made for the 

 formation of the opening before it was accomplished. 

 Alt. -053 in., diam. '078. (Watson.) 



The peculiarity of the outer lip in its relation to the umbilicus in 

 in this and the preceding species, a feature which often occurs also 

 in the fossil genus (Trochotoma), will probably offer a sub-generic, 

 or even generic distinction, for those who love to multiply our 

 difficulties of nomenclature. (Watson.) 



Off Culebra Island, West Indies, in 390 fms. 



Schismope lacuniformis, WATSON, Challenger Rep., Gasterop., p. 

 118, t. 8, f. 8, 1886. 



