Cocculiim.] GASTROPODA. 173 



small or moderately raised central tooth, 3 moderate inner laterals 

 with denticulate cusps, a larger denticulate major lateral with a stout 

 and twisted stalk, and on each side a stout base from which spring 

 numerous slender marginals hooked at their tips. There is no jaw. 



Shell patelliform, not nacreous, symmetrical, with an entire non- 

 sinuated margin and a posteriorly inclined apex with a (usually 

 deciduous) spiral nucleus ; muscular impression horseshoe - shaped, 

 interrupted over the head. 



Genus 1. COCCULINA, Dall, 1882. 



Cocculina, Dall.. Proc. U.S. Nat, Mus., 1881 (1882), 402. Type: C. Kath- 

 buni, Dall. Cocculina, Dall, " Blake " Gastropoda" 345 ; Man. 

 Conch. (1), xii, 131. Tectura sp., Jeffreys, P.Z.S., 1882, 672. 



The shell is colourless, with radiating and concentric sculpture ; 

 other characters are those of the family. 



Anatomy. Dr. Joh. Thiele, ' Die beschalten Gastropoden der 

 deutschen Tiefsee Expedition." B. Anatom. Systemat. Untersuch. 

 einiger Gastropoden, 149-56, pi. 6, f. 1-22. 



Distribution. North Europe, north-eastern and western Atlantic, 

 Indian Ocean, Philippines, Australasia. Deep-sea forms. 



KEY TO SPECIES. 



A. Margin in one plane. 



a. Shell with minute concentric and radiate threads . . tasmanica. 

 aa. Shell with the sides subparallel, surface distinctly cut 



up into granules by concentric and radiate sculpture craticulata. 



B. Margin raised at both ends. 



. Shell laterally compressed, summit anterior. . . . compressa. 



aa. Shell not laterally compressed, saddle-shaped, summit 



slightly posterior . . . . . . . . clypiddlceformis. 



1. Cocculina clypidellaeformis, Suter, 1908. Plate 34, figs. 13. 13. 

 Cocculina clypidellceformis, Suter, P. Mai. S., viii, 27, pi. 2, f. 19, 20. 



Shell minute, having the shape of a Clypidella i.e., saddle-shaped 

 the sides descending, and the anterior and posterior margin slightly 

 elevated ; thin, translucent, smooth, apex slightly posterior. Sculp- 

 ture consisting of concentric growth-lines only ; they are fine and 

 microscopic on the upper half, more conspicuous and irregular to- 

 wards the base. Colour white. In the young shell the nucleus is 

 minute, globose, and polished ; adult shells have usually lost it. The 

 summit is very little behind the middle in the adult roundish shell, 

 but nearly at the posterior third in the young more oval shell ; it 

 is slightly raised, the anterior, posterior, and the lateral slopes are 

 uneven, moderately convex. Interior greenish- white ; muscular im- 

 pression very distinct, forming a half-circle. 



Length, 2-8 mm. ; breadth, 2-5 mm. ; height, 2-2 mm. 



Animal unknown. 



Type in my collection. 



Hob. Snares, in 50 fathoms (Captain Bollons). 



