SCISSURELLA. 53 



This differs from any other species known to me in being devoid 

 of sculpture, and in having a conspicuous umbilicus. (Jeffreys.^ 



Scissurella umbilicata JEFFREYS, P. Z. S. 1883, p. 88, t. 19, f. 1. 

 S. TENUIS Jeffreys. 



Shell forming a depressed cone with an expanded base, sloping to 

 the periphery and slit, very thin, scarcely transparent, and rather 

 glossy ; sculpture, extremely numerous and fine curved longitudinal 

 strise, and equally numerous and fine concentric or spiral striae, which 

 by their intersection cause a regular but minute cancellation; the 

 concentric strise at the base are stronger and more distinct than the 

 longitudinal strise ; the sculpture is of course interrupted by the 

 peripheral slit and groove ; color pearly white ; spire greatly depressed ; 

 whorls 5, somewhat flattened below the suture ; the last enormously 

 exceeds in size all the others put together ; slit central, long and 

 broad ; groove also broad, marked across by regular but rather 

 distant curved strise ; edges sharp and upturned ; mouth obliquely 

 oval; outer lip thin; inner lip folded back and curved; pillar 

 nearly straight, having a twisted fold in front of the umbilicus, which 

 is small and narrow. Alt. O25, diam. 0*2. (Jeffreys.) 



North Atlantic. 



This differs from S. crispata and its varieties in its depressed shape, 

 thinner texture, more*delicate sculpture, the larger size of the last 

 whorl in comparison with the others, the pillar being furnished with 

 a fold, and in its narrower umbilicus. (Jeffreys.) 



Scissurella tennis JEFFREYS, Ann. and Mag. Nat. Hist., 4th series, 

 vol. 19, p. 234. 



S. CONICA d'Orbigny. PI. 57, figs. 8, 9. 



Shell orbicular-conic, globulose, pellucid, transversely lamellose- 

 ribbed ; spire elevated ; carina wide ; aperture rounded ; umbilicus 

 large. Alt. 2 mill. ( Orb.) 



Falkland Is. 



S. conica ORB., Voy. dans 1'Amer. Merid., p. 470, t. 78, f. 7-9. 

 PHILIPPI, Conchyl. Cab., p. 35, t. 6, f. 4. 



S. BERTHELOTI d'Orbigny. PI. 58, fig. 26. 



Shell orbicular-depressed, vertex a little flattened, transversely 

 striate-costate above, striate below ; spire depressed ; whorls 3, 

 rounded ; carina broad, acute ; aperture orbicular ; lip thin, acute ; 

 umbilicus open. Slit fasciole smooth ; color bistre-brown. ( Orb.) 



Teneriffe, Canaries. 



