SCHISMOPE. 65 



S. CARIXATA Watson. PL 6$, figs. 17, 18, 19. 



Shell tumid, but depressed, finely ribbed and strongly keeled, 

 with a flattened but scalar spire, convex whorls, a minute apex, a 

 tumid base, and a large funnel-shaped, shallow, carinated umbilicus 

 Sculpture: there are both above and below sharp, little, distant, 

 curved, radiating riblets, between which the whole surface is exquis- 

 itely scratched with microscopic lines. Spirals : there is a strong, 

 rounded, expressed double keel, formed by the two edges .of the 

 canal scar, which encircles rather more than the whole of the last 

 whorl (except near the mouth); this canal is sunken and is strongly 

 scored. Above the canal the surface is smooth, but a few micro- 

 scopic spiral threads exist ; below and remote from this canal there 

 are on the base three strong, round to square threads, of which the 

 highest is the strongest, and tends to become flattened and expanded 

 into a great spiral fold of the shell rather than a mere thread ; 

 besides these another similar but weaker encircles the umbilicus. 

 Color hyaline, but hardly glossy. Spire slightly exserted, the 

 whorls being flat on their upper surface, and rising roundly from 

 the suture. Apex very small, tabulated. Whorls 4, of very rapid 

 increase, very strongly keeled by the canal-ridge, and angulated by 

 the largest and highest thread ; the base is very tumid. Suture 

 rectangular. Mouth oval, very oblique. Outer lip runs in straight 

 lines and angles, but is somewhat curved on the base. Inner lip 

 very thin and very short on the body, extremely retiring, being cut 

 quite away, so as to completely expose the umbilicus, concave on 

 the pillar, where it is sharp edged ; in front it is subfcruncate and 

 slightly twisted, but passes on into the outer lip-edge at the umbili- 

 cal carina. Umbilicus large, defined by a keel, shallow. Puncture 

 very long and narrow, blunt and rounded at the upper end, and 

 extending to a long fine point in front ; it opens on the top of a 

 swollen ridge ; it has no projecting lips on the inner side of the shell, 

 but is produced there in a long narrow furrow. 



Alt. -052 in., diam. '062. ( Watson.) 



The young of this species, it is almost certain, will be taken some 

 day for a Trochus, and the adolescent for a Scissurella, the great 

 length of the old canal and the open foramen being peculiarly 

 deceptive. In this state, when nearly full grown, it is singularly 

 like S. costata, D'Orb., from the Mediterranean, but its sculpture is 

 5 



