254 MOLLUSCA OP THE ' CHALLENGEB ' EXPEDITION. 



W. of Azores. 1000 fms. Gloligerina-ooze. Bottom-tempe- 

 rature 39°-4. 



Shell. — Very higli and narrow, conical, scalar, ribbed, bluntly 

 keeled, with a very short conical base. Sculpture. Longitudinals 

 — below the suture is a double collar of 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 

 rows 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 

 YBTj high and narrow, scalar. Apex broken. Whorls : only 5 

 remain ; they are high and narrow, di'oopingly 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 swoln, 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. 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 generic sinus exists merely in the form of 

 a very slight retreat of the lip from the suture to the keel. 

 In classing it with Cliooiella I have followed the advice and 

 example of Mr. E. A. Smith, while Adams regards that group as 

 freshwater and allied to Melania. The name is derived from the 

 very remarkable structure of the shell, which consists of 4 layers : 

 the inmost of these is porcellaneous 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. 



