474 REV. R. ROOG WATSON ON THE 



the middle of the whorls, and are obliquely and feebly produced 

 to the inferior suture ; they are obsolete on the base : the sur- 

 face is closely scratched with fine, somewhat unequal lines of 

 growth. Spirals — there is a very slight pad which forms an infe- 

 rior margin to the suture ; below this is a hardly concave furrow, 

 on the lower side of which the whorls are angulated by the 

 projection of the tubercles : the lower part of the whorls is very 

 obsoletely marked with broad flat spiral threads, which may be 

 traced to the tip of the snout. Colour pale waxy white, whence 

 the name. Spire conical, with profile-lines interrupted by the 

 prominence of the keel, from which both above and below is a 

 contraction into the suture. Apex consists of 2 tumid rounded 

 whorls of nearly equal size, with a very slight suture. Whorls 

 8 in all, of slow and regular increase ; the last is small, with a 

 rounded conical base and a smallish snout : they are angularly 

 convex, with a slight contraction into the suture, both at top and 

 bottom of the whorls. Suture a little impressed, rather oblique. 

 Mouth small and narrow, pear-shaped, scarcely angulated above, 

 and drawn out into a rather narrow canal in front. Outer lip 

 regularly curved above, flat . in front : the edge retires slightly 

 below the suture, so as to form the deep rather narrow sinus, 

 whose lower side is made 'by the very high and prominent 

 shoulder, which advances very far forward, and still continues to 

 do so though more slightly on to the edge of the canal, where it 

 again retires to the left. Inner lip : there is a thin glaze on the body 

 and pillar whose union is very slightly concave : the generic fold is 

 a prominent, rounded, narrow thread which coils round the pillar 

 about the middle and parallel to the suture : the front of the 

 pillar is narrow, twisted, and oblique. H. 0*5. B. 0*2. Penul- 

 timate whorl, height 008. Mouth, height 023, breadth 009. 



It is interesting to add a new species, and that from the 

 Atlantic, to the few living Pacific species of this Tertiary fossil 

 genus. The whole aspect of the shell is that of a Pleurotoma of 

 the Surcula group. 



64. Pleurotoma (Borsonia) silicea, n. sp. 



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

 Off Pernambuco. 350 fms. Mud. 



Shell. — High, narrow, biconical, with a tall, blunt, scalar 

 spire, and a short contracted base : whorls angulated, but hardly 

 prominent above, tubercled but scarcely ribbed, obsoletely 

 spiralled. Sculpture : there are in the middle of the whorls small 



