MOLLTJSOA OF THE * CHALLENQER ' EXPEDITION. 261 



minent pointed base and a small raised scalar spire, in a way 

 that is very peculiar, so much so, indeed, that it almost recalls an 

 Amphibola. A. tenuis, Gray, in particular, has features of re- 

 semblance. It very slightly resembles N~. nana, Mdller, from 

 Greenland ; but the body- whorl is more depressed, the spire is 

 more exserted, and the umbilicus is not closed, as in that species. 



7. Natica leptalea, n. sp. (XeirraXeos, delicate.) 



St. 23. March 15, 1873. Lat. 18° 24' N., long. 63° 28' W. 

 Off Sombrero Island, St. Thomas, Danish West Indies. 450 fins, 

 Glohigerina-oozQ. 



Shell. — Delicate, depressedly globose ; spire slightly scalar, 

 but with a flat round apex, thin, smooth and glossy, ivory-white, 

 umbilicated. Sculpture. Longitudinals — very delicate hair-like 

 lines of growth. Spirals — the whole surface is covered with very 

 faint, minute, and superficial lines and furrows, complicated with 

 sharper wavy microscopic scratches ; the two so run into one 

 another that it is difficult to say how far they are distinct, only 

 they are so. Colour uniform ivory-white. Epidermis : none 

 visible. Spire rises in a series of rounded steps from the inferior 

 whorls. Apex large, but depressedly rounded. Whorls 4J ; the 

 first 1| are embryonic, tumid, and equably rounded, of rather rapid 

 increase. Suture very little oblique, slightly channelled. Mouthyery 

 oblique, roundly oval to circular, with a flattening of the left side ; 

 its height is rather more than five sevenths of the whole height. 

 Outer lip open and well rounded throughout its whole sweep ; its 

 edge is thin. Inner lip is flatly curved ; it spreads thinly across 

 the body, is thinly reverted on the umbilicus, which it narrows 

 but does not close, retreating at this point gradually to the pillar, 

 where it is slightly nicked by the intraumbilical furrow ; below 

 this it is a little thickened and reverted throughout the length of 

 the pillar. Umbilicus, which is small and funnel-shaped at its 

 mouth, is not defined by any carina ; within it is a slight furrow; 

 it is half covered by the reverted lip, and contracts at once to a 

 mere pore. H. 0*35. B. 0*33. Penultimate whorl, height O'll. 

 Mouth, height 0*26, breadth 02. 



This species resembles some of the more flattened forms of the 

 young of N. Montagui, Forb. ; but than that species this is less 

 globose, more depressed, with a higher, shorter, blunter spire, the 

 apex of which has much coarser whorls ; the mouth is much 

 larger, more circular, and is not obliquely turned in under the 



