Naviculacea.] infusoeial animalcules. 351 



DiscoPLEA (?) undata — Sui-facc covered by minute granules in 

 radiating series ; margin undulate, with fifteen sinuosities. Diameter 

 l-576th. Bermuda. 



D. (?) Penuina.—^\ixh.cG of disc rayed ; five fine rays reaching as 

 far as the centre. The thickness of the bivalve testule equals half 

 its width. Has the habit of D. astrcea, and of Oallionella varians. 

 Diameter 1 -600th. Found in the pumice from Arcquipa and 

 Santiago, Peru. 



D. (?) Eota — Disc large, surface unequally papillose ; central 

 papillae largest ; margin with fifty-two equal rays not attaining the 

 centre; their intervals occupied with scattered papillse. Diiameter 

 1-1 92nd. It approaches Actimptyclim dives, to which, along with the 

 ensuing species, it may be perhaps united in a new genus. A gela- 

 tinous envelope is not apparent ; and true septa are wanting. 



D. (?) Rotula. — Disc smaller than the preceding, covered with 

 small scattered and equal papillae ; margin with twenty equal rays 

 not reaching the centre. Diameter l-696th. Southern Ocean. 



D. (?) dives = AdinoptycJius dices =^ Cyclotclla dives (Kiitz.) — Is re- 

 markable by the rows of papillae in the intervals of the rays, and 

 the smaller ones at the centre. Diameter l-812th. 



D. (?) Coseinodiseus. — Small ; ^>?c irregularly but densely and 

 fiinely granular ; margin smooth. Habit of Coseinodiseus minor, 

 rather turgid on the side. Diameter 1-1 728th. Fossil, New Hampshire. 

 D. (?) physoplea. — Small ; disc and margin smooth j with a cir- 

 ciunscribed centre to the disc, bearing twelve large, vesicular-looking 

 granules; limb, broad and smooth. Diameter 1-1 152nd. Fossil, 

 Virginia. 



D. mammilla. — Smooth, thick, nummiform (money-shaped), 

 suture of the valves tumid ; centre of the disc of each valve raised as 

 a boss (umbo) ; marginal ring vanishing ; suture dentated on the side 

 of each valve. Diameter 1-86-lth. Fossil on the coast of Patagonia. 

 D. (?) cingulata. — A fossil species from ^gina, so named by 

 Ehrenberg. 



D. radiata. — Also a fossil species from the same locality. 

 D. atinospherica. — Margin of disc plane, mth broad and equal 

 radiations ; central portion rather turgid and granular, naiTower 

 than the striated border ; the granules and the striae becoming con- 



