REPOET ON THE GASTEROPODA. 371 



small close-set tubercles prolonged downward into folds ; below these at the keel are 

 swellings, whence descend flat, rounded, rather feeble ribs, which die out before they 

 reach the lower suture ; the surface is closely scored with unequal straight lines of 

 growth. Spirals — there are very many strongish rounded threads parted by fine shallow 

 furrows of equal width ; these are crowded on the shoulder. On the middle of the body- 

 whorl a feebler thread appears, like a shadow in the furrows. Colour : it is bleached 

 dead white. Spire very high and narrow, scalar. Apex broken. Whorls : only 5 

 remain ; they are high and narrow, droopingly shouldered above, bluntly keeled, 

 cylindrical, but contracting from the keel to the lower suture ; the last is narrow, small, 

 and cylindrical, but a very little swollen, with a short very one-sided conical base. 

 Suture strong, irregular, a little constricted. Mouth narrowly oval, small, bluntly 

 pointed above. Outer lip flatly arched. Inner lip slightly excavated, concave above, 

 with a straight, shortish, and strong pillar. H. 1*9 in. B. 0'57. Penultimate whorl, 

 height 0-38. Mouth, height 0"8, breadth 0-35. 



This is a singularly attenuated form of great beauty, unhappily much broken. The labral sinus 

 exists merely in the form of a very slight retreat of the lip from the suture to the keel. In classing 

 it with Clionella I have followed the advice and example of Mr E. A. Smith, while Adams regards 

 that group as freshwater and allied to Mclania. The specific name is derived from the very remarkable 

 structure of the shell, which consists of 4 layers : the inmost of these is porcellanous and very thin ; 

 the next is made up of spiral fibres ; the third consists of longitudinal fibres (both of these being 

 comparatively thick), while the outside is membranaceously cretaceous. 



2. Clionella exsculpta, Watson (PI. XXIV. fig. 2). 



Pleurotonia (Drillia) exsculpta, Watson, Prelim. Report, pt. 11, Journ. Linn. Soc. Lond., vol. xvi. 



p. 247. 



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. 



Shell. — High, narrow, conical, scalar, ribbed, with a sub-contracted conical base, a 

 bluntish apex, and having the colour of thin pale flint. Sculpture : Longitudinals — on 

 the last whorl there are about 20 (on the first regular whorl about 12) narrow rounded ribs, 

 which originate in the suture ; just below this they rise into little rounded tubercles ; 

 at the periphery they project in larger and slightly elongated tubercles, below this point 

 they become slightly oblique, are feebler on the base, and disappear on the snout : the 

 lines of growth are fine, but irregular and somewhat indistinct. Spirals — below the suture 

 a slight rounded thread connects the costal tubercles ; at the peripheral row of tubercles is 

 a keel ; feeble, remote, rounded threads appear on the whole surface, becoming stronger 

 on the base, and still more so on the snout. Colour that of pale flint when seen in thin 

 flakes. Spire high, narrow, conical, scalar. Apex consists of 1^ embryonic whorls, which 



