. EEPORT ON THE GASTEEOPODA. 291 



19. Pleurotoma (Surcula) goniodes, 1 Watson (PI. XX. fig. 5). 



Pleurotoma (Surcula) goniodes, Watson, Prelim. Report, pt. 8, Journ. Linn. Soc. Lond., vol. xv. 



p. 394. 



Station 320. February 14, 1876. Lat. 37° 17' S., long. 53° 52' W. South-east 

 of the Kio de la Plata. 600 fathoms. Green sand. Bottom temperature 37 "2°. 



Shell. — Hio-h, narrow, biconical, subscalar, with a long, uneonstricted base and a 

 subequal-sided snout, angulated, with an expressed keel, and with regular fine spiral 

 threads all over. Sculpture : Longitudinals — there are only fine, regular, close, hair-like 

 lines of growth. Spirals — in the middle of each whorl is a strong angulation formed by 

 the straight drooping line of the shoulder and the straight contracting line down to the 

 inferior suture ; the angulation is pinched out into a sharp round-edged keel ; there are 

 fine sharpish threads on the whole surface pretty equally distributed and of equal 

 strength ; of these there are on the penultimate whorl below the keel about 6 ; they are 

 parted by flat broadish intervals, strongly scored with the lines of growth. Colour white 

 under a yellow epidermis. Spire high, narrow, conical, with profile-lines interrupted by 

 the straisht-lined contraction of the shell between the keels of the successive whorls. 

 Apex (eroded) small and rounded. Whorls 6-7 ; their profile consists of two straight 

 lines meeting in the keel which bisects the whorls ; above is a slowly sloping shoulder, 

 and below a gradual contraction to the suture ; the last whorl is scarcely convex on the 

 conical base, which contracts with great regularity to the long, nearly equal-sided snout. 

 Suture fine, linear, but well defined. Mouth club-shaped, being rhomboidal above, with 

 a long narrow canal below. Outer lip high-arched and then straight along the canal ; its 

 edge retreats at once to the left, and forms a remote, deep, rounded sinus in the shoulder 

 above the keel ; below this it sweeps out into a high and prominent shoulder. Inner lip 

 little concave at the junction of the body and pillar, which is straight above, but towards 

 the point is obliquely cut off with a long, narrow, twisted edge, and bends a good deal to 

 the left. H. 0-9 in. B. 0'38. Penultimate whorl, height 0'16. Mouth, height 0'51, 

 breadth 0-22. 



This is a stumpier form than Pleurotoma leucotropis, Adams and Reeve, with a more conical and 

 less constricted base, and shorter and more bent snout. From Pleurotoma oxytropis, Sow., while 

 differing, of course, still more markedly in most of these points, it differs yet more in sculpture. 

 Though a much smaller and narrower form and with a more conical and less tumid base, it is in a 

 general way very like Pleurotoma circinata, Dall ; but that is destitute of the spiral sculpture on 

 the shoulder, which seems also to be the case with Pleurotoma kennicottii, Dall, a smaller form than 

 Pleurotoma circinata, and which is also distinguished by a double keel on the last whorl. 



i ytaifiubri;, angular. 



