450 REV. R. BOOG WATSON ON THE 



whorls) 1-03. B.0-35. Penultimate whorl, height 021. Mouth, 

 height 0-49, breadth 018. 



This very remarkable form, suggestive of the Narwhal's horn, 

 has unfortunately lost its whole apex. If, therefore, I have put 

 it in this group, it is that the whole style of the shell rather 

 suggests this companionship ; and at least I prefer to put it here 

 than under Surcula or Defrancia. It has in form some features 

 of resemblance to P. aureola, Reeve, from the Philippines ; but, 

 apart from colour, it has a deeper suture and rounder whorls 

 than that. 



48. Pletjrotoma (Thesbia) papyracea, n. sp. 



St. 147. December 30, 1873. Lat. 46° 16' S., long. 48° 27' E. 

 Between Prince Edward Islands and Kerguelen. 1600 fms. 

 Glooigerina-ooze. Bottom temperature 34 0, 2. 



Shell. — Thin, like delicate tissue-paper, white, bluntly keeled, 

 subplicate, with a small, high, sharp, scalar spire, an angulated 

 suture, a short tumid body-whorl narrowing from the carina, 

 suddenly contracted on the base, and prolonged into a largish 

 triangular one-sided snout. Sculpture. Longitudinals — there are 

 extremely fine hair-like lines of growth ; there are also oblique, 

 rounded, narrow foldings of the surface, which below the sinus- 

 area rise into 14 small, narrow, sparse ridges or elongated tuber- 

 cles and extend to the base : on the earlier whorls these rise into 

 small thread-like ribs which reach the inferior suture. Spirals — 

 the almost membranaceous sinus-area forms a sloping shoulder 

 below the suture, and occupies about one third of the whorl ; below 

 this is the keel, on which the little tubercles rise : from this keel 

 downwards the surface is covered with minute, unequal, but rather 

 regular, though somewhat interrupted, sparse threads with broader 

 intervals : besides this there is a microscopic, obsolete, spiral gra- 

 nulation which extends to the sinus-area. Colour alabaster- white, 

 so far as the excessive thinness permits ; the small spiral threads 

 are somewhat dead white ; the embryonic whorls are of a rich 

 ruddy-orange tint. Spire perfectly conical, scalar, high, sharp. 

 Apex consists of 3| ruddy, smooth, embryonic whorls, which are 

 globose, divided by an impressed suture, and rise to a small, blunt, 

 round top, in the middle of which the extreme tip just barely 

 rises into sight. Whorls 8^- in all, of slow, but increasingly 

 rapid enlargement ; those of the spire are rather narrow and 

 high, and have a high flat shoulder, a sharp angulated keel, and 



