KEPOKT ON THE GASTEROPODA. 347 



a very slight drooping shoulder defined by the tubercled spiral thread and keel which 

 bisects the earlier whorls, but loses importance in all ways further down ; below this keel 

 there is a slight gradual contraction into the inferior whorl ; the last whorl is very slightly 

 tumid, with a protracted, slightly convex base produced into a narrow snout. Suture a 

 little impressed, marginated below by the infrasutural thread, whose upper edge forms a 

 minute horizontal shelf, and which looks as if it girt-in the shell. 1 Mouth long, narrow, 

 pear-shaped. Outer lip thin and sharp, steeply curved above, slightly convex below ; the 

 edge advances below in a full round sweep ; above it forms a prominent, but not very high 

 shoulder, above which lies the open rounded sinus, with a minute triangular shelf formed 

 by the projection of the infrasutural thread, and to a small extent separating the sinus 

 from the body. Inner lip narrow, shallowly excavated in the substance of the shell, dying 

 out early in front on the oblique, sharp but rounded, twisted and slightly reverted edge 

 of the pillar. H. 0'5 in. B. 0-18. Penultimate whorl, height 0"08. Mouth, height 

 0-28, breadth 0*09. 



This species and Pleurotoma (Mangelia) macra, Wats., belong to a group very peculiar, and 

 evidently numerous in the North Atlantic, as there are young specimens of five other species from 

 the same neighbourhood, evidently all distinct, but stamped strongly with the same features, of a 

 thin glossy shell, obsolete sculpture, a slight gemmate keel, and the peculiar large, conically globose, 

 minute-tipped, smooth, longitudinally ribbed apex. 



77. Pleurotoma [Mangelia) tiara, Watson (PI. XXI. fig. 7). 



Pleurotoma (Mangelia) tiara, Watson, Prelim. Report, pt. 9, Journ. Linn. Soe. Lond., vol. xv. p. 440. 



Station 24. March 25, 1873. Lat. 18° 38' 30" N., long. 65° 5' 30" W. North of 

 Culebra Island, West Indies. 390 fathoms. Pteropod ooze. 



Station 56. May 29, 1873. Lat. 32° 8' 45" N., long. 64° 59' 35" W. Off Bermuda. 

 1075 fathoms. Coral mud. Bottom temperature 38 0- 2. 



Shell. — High and narrow, rather strong, white, spiralled, with a high subscalar spire 

 ending bluntly in a small tip, with a very small body-whorl, a short contracted base, and 

 a very short small snout. Sculpture: Longitudinals — there are a number of hair-like 

 sinuous lines, which in the sinus-area are like bars ; they are parted by flat intervals of 

 about three or four times their width : the lines of growth are very faint. Spirals — there 

 are on each whorl two strong sharp keels which nearly trisect the whorl ; the lower of 

 these is sometimes feeble ; marginating the suture below is a fine thread ; on the base are 

 8 or 10 sharp and prominent threads of varying and unequal strength ; at the upper end 

 of the snout is another strong thread ; below this is a little furrow, answering, as in Ceri- 

 thiopsis, to a small nick at the point of the pillar. On the pillar are from two to four 



1 Hence the name. 



