BASILISSA. 421 



Gasterop., p. 384. — Seguenzia delicatula Dall, Bull. M. C. Z. ix, p. 

 48, 1881. — B. alta var. delicatuln Dall, 'Blake' Gasterop., p. 384, 

 t. 22, f. 2. 



Var. OXYTOMA Watson. PL 36, fig. 4. More distinctly sculpt- 

 ured. 



Var. DELICATULA Dall. PI. 48, figs. 3, 4. More delicate and 

 thin than the type, but otherwise much like it, except that the 

 delicate spiral threads cover the whole surface of the shell. {Dall.) 



B. LAMPRA Watson. PI. 36, figs. 10, 11. 



Shell thin, white opalescent, smooth, faintly reticulated, with a 

 high concave spire, sharp apex, acute carina, angulated umbilicus, 

 and rhomboidal mouth. Sculpture : smooth, glossy, iridescent, with 

 ten to twenty faint spiral threads on the upper side of the body- 

 whorl ; the last of these which joins the lip is much stronger than 

 the others ; a little remote and below is a thread forming the keel, 

 below which, and nearer, are two other strong threads ; round the 

 umbilicus are also two strong threads ; the intermediate space on the 

 base is marked with eight to ten impressed spiral striae. The inter- 

 stices of the spirals are crossed by longitudinals, which are regular, 

 fine, hair-like but distinct and well parted ; their curve on the 

 surface below the suture shows the old sinus. On the base they are 

 radiating and are crowded and irregular, except around the 

 umbilicus where in the first two or three striae they are very sharp 

 and distinct. On the upper whorls both the spirals and longitudinals 

 are finer, but sharper than they are on the last. Color grayish, 

 horny, translucent, opalescent white. Spire raised, with a concave 

 outline. Apex, which consists of the single minute embryonic 

 wdiorl, is slightly exserted and sharp ; it is quite smooth, but the 

 spirals and longitudinals begin sharply immediately below it. 

 Whorls 65 ; the earlier ones are of slow and regular increase, 

 depressed, quite flat on their side lines ; the last widens rapidly, is 

 slightly rounded above, and still more slightly concave on the base, 

 with an acute, but still rounded keel. Suture impressed on the 

 body-whorl, but on the upper whorls sharply, though slightly, mar- 

 ginated below. Mouth a little oblique, rhomboida', the basal and 

 palatal lines being nearly parallel, while the outer and inner lips 

 diverge downwards. Outer lip thin, not patulous, not descending, 

 advancing at its insertion, and then retreating so as to form a shallow, 

 broad, open sinus a little below the suture, acutely but roundedly 



