468 RET. R. BOOO WATSON ON THE 



and St. 85 ; but all the specimens are very young. From its 

 reticulated sculpture I had called it P. (Defrancia) cribraria. 

 There is another ' Challenger' species it resembles from St. 73, 

 and for which I had chosen the name P. (D.) smileufa, unfor- 

 tunately also a young specimen. The distinction between the 

 present species and these others is expressed by the name 

 cliyta (xvros, cast); while P. (D.) smileuta (ajjuXevrbs, chipped 

 out) is like a thing blocked out of the solid. P. (D.) formosa, 

 Jeff., again resembles something on which superficial ornament 

 has been laid and attached by melting. In all three cases there 

 is a resemblance in the forms and sculpture ; but under that 

 resemblance there is the strongest difference. 



59. Pleurotoma (Defrancia) perpauxilla, n. sp. 



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

 N. of Culebra Island, St. Thomas, Danish W. Indies. 390 fms. 

 Coral-mud. 



Shell. — Yery small, high and narrow, white, ribbed and spiralled, 

 with convex whorls, a small elongated regular body, impressed 

 suture, a high, conical, small-tipped spire, a rounded base, and a 

 small, longish, triangular, one-sided snout. Sculpture. Longitu- 

 dinals — there are on the latter whorls about 9 biggish flatly 

 rounded ribs, parted by equally broad open rounded furrows ; in 

 the upper whorls they barely reach the lower suture ; on the 

 last they hardly extend to the base ; they originate at a shoulder 

 below the sinus-area ; they are thus very short. The lines of 

 growth are very faint, except in the sinus-area, where, round the 

 top o£ the whorls, the old sinus-scars form a series of short, sharp, 

 regular, remote, little riblets. Spirals — below the sinus-area is a 

 feeble thread ; the periphery of the whorls is marked by two 

 sharp, square-topped threads, which form a double keel ; the 

 upper one is very near the feeble thread above mentioned : the 

 interval between the carinal threads is about four times their 

 breadth ; somewhat more remote, a third thread, equally strong, 

 appears on the last whorl, coming out exactly from the oral 

 angle and defining the base ; above and below this, at about equal 

 distances, are two feebler threads ; the rest of the base is bare, 

 but the entire snout is covered with very small spiral threads. 

 The entire surface is very minutely scored with microscopic spiral 

 lines. Colour frosted white, with a buff apex. Apex : there are 



