MOLLUSCA OF THE ' CnALLENGER ' EXPEDITION". 31 



2. PUNCTUEELLA (CE/i-NOPSIs) GRAISTULATA, Seg. [tUBEKCULATA, 



11. sp.] 



St. 24. March 25, 1873. Lat. 18°38'30"N., long.65°5'30" AV. 

 Off St. Thomas, north of Culebra Islaud, Danish W. Indies. 

 390 fms. Coral-nmcl. 



Segueuza, ' Palseont. Malac. Terr. Terz. di Messina,' p. 14, 

 pi. V. f. 6 {Bimida). 



Shell. — Porcellaneous white under a meagre j^ellow epidermis, 

 rather thin, narrow, broader in front, oblong, with a depressed 

 and reverted top and incurved apex ; the side slopes are steep 

 and slightly convex, the front edge is long and very convex, 

 the back slope is concave in consequence of the overhanging 

 apex ; the small close-set radiating ribs are beaded with conti- 

 guous small rough tubercles ; the long narrow fusiform slit 

 rises very high, and is remote from both apex and margin. 

 Sculpture. Erom the a^iex over 100 small irregular and unequal 

 riblets radiate to the margin ; they are closely beset with small 

 rough tubercles like threads ; there are no concentric threads, 

 but a few unequal lines of growth can be seen ; the riblet which 

 runs from the slit is double, with a minute furrow between the 

 riblets ; its direction is not quite constant in different specimens. 

 Colour : the shell is pure white, porcellaneous under the thin 

 straw-yellow membranaceous epidermis, which is rather caducous. 

 Apex very much reverted and depressed so as to stick out back- 

 wards bluntly, but prominently in the mid line of the shell ; the 

 minute smooth white tip stands out on the right with considerable 

 distinctness, completing a regular spire of 2| whorls in all. Slit 

 stands very high, its upper end rising to the crest of the shell, 

 though still remote from the apex ; it is long, narrow, and deep, 

 and tapers off at both ends ; the old scar is deep and narrow. 

 Marffin thin and sharp, toothed all round, but hardly crimped 

 within ; behind it is very patulous, but elsewhere the internal slope 

 is very steep ; the two sides are very straight and converge back- 

 wards. Inside porcellaneous, deeply hollowed into the apex ; a 

 sharp little furrow that resembles a crack runs up from the 

 margin to the slit, Avhich is almost quite covered in all its length 

 by the patulous but small and flatly arched imbuttressed septum. 

 L. 0-31. B. 019. H. 015. 



This species is peculiarly long and narrow, and roomy within 

 from its steep walls and blunt apex. Its sculpture, too, is very 

 striking. 



