422 REV. R. BOOG WATSON ON THE 



with a narrow, rounded, but scarcely twisted edge. H. 0*24. B. 

 0*117. Penultimate whorl, height 0*04. Mouth, height 012, 

 breadth 0'06. 



This shell may very likely be immature. The external lip in 

 Pleurotoma is generally so thin that it is difficult to determine 

 from it when the shell is full-grown. 



24. Pleurotoma (Drillia) stirophora, n. sp. (oretpo^opos, 

 keeled.) 



St. 122. Sept. 10, 1873. Lat. 9° 5' S., long. 34° 50' W. Per- 

 nambuco. 350 fms. Mud. 



Shell. — High, narrow, with an elongated conical base, longish 

 pillar, and a blunt apex, angulated, obsoletely ribbed, tubercled, 

 thin, polished, flinty white. Sculpture. Longitudinals — the lower 

 half of the whorls is crossed by obsolete, rounded, oblique, straight 

 ribs, with very slight rounded depressions between ; there are 

 about twelve, of increasing indistinctness, on the last whorl, and 

 nine on the first regular whorl ; they take their origin in a row of 

 small, round, sharpish tubercles ; they do not extend to the base. 

 The lines of growth are faint sharpish scratches, and are quite 

 independent of the ribs. Spirals — a little above the middle each 

 whorl is angulated and carinated, the carinal thread being set with 

 small, sharpish-pointed tubercles, in which the longitudinal ribs 

 originate. The sinus-area is smooth ; the rest of the surface is 

 marked by very obsolete, depressed, rounded threads. Colour 

 greyish transparent white. Spire high, narrow, conical ; its pro- 

 file-lines but little interrupted by the broad, shallow, sutural de- 

 pression which extends from keel to keel of the successive whorls. 

 Apex consists of nearly 2 embryonic whorls, which are cylindrical, 

 quite smooth, and end in a perfectly rounded tip, which is slightly 

 immersed, and scarcely, if at all, oblique. Whorls 7, short, and of 

 slow increase ; they are angulated above the middle, with a droop- 

 ing, scarcely hollowed shoulder above, and a very slight contrac- 

 tion of their straight line below ; the last is small, rapidly con- 

 tracted on the conical base, and running out into a somewhat 

 one-sided, and slightly twisted, narrow, longish snout. Suture 

 little oblique, linear, a little disturbed by the longitudinal ribs ; 

 well defined by the superior and inferior slope of the whorls. 

 Mouth club-shaped, oval above, with a longish, open, rather ob- 

 lique canal. Outer lip thin, with a flattened convex curve, which 

 is steepish at the shoulder and elongated at the canal ; on 



