404 DE. G. S. BRADY ON THE OSTEACODA 



behind, height equal to nearly half the length ; anterior extremity rounded, subtruncate ; 

 posterior produced in the middle into a very acute beak, the upper half being obliquely 

 truncate and jagged, the lower half excavated into two large rectangular indentations; 

 dorsal margin straight, ventral slightly sinuated. Outline as seen from above lancet- 

 shaped, with a large triangular projection in the middle, behind ; widest behind the 

 middle, width equal to nearly two thirds of the length ; the anterior extremity is 

 pointed and broadly rounded, as a lancet ; lateral margins nearly straight to near the 

 hinder extremity, then suddenly sinking so as to form one and then a second rectan- 

 gular excavation ; posterior extremity acuminate. End view irregularly arcuate, width 

 considerably greater than the height ; surface of the shell irregularly waved and 

 nodulated, the posterior portion marked by two prominent and sharply defined trans- 

 verse ridges, which end below in sharp rectangular processes, and above are continued 

 in longitudinal curves toward the middle of the valves. Length -^ inch (0'60 millim.). 

 A few specimens only found, in the Pectuncuhcs-hed (Sables inferieurs) and zone a 

 Bryozoaires (Sables moyens). It has been found by M. Bosquet in several Eocene 

 deposits in France and Belgium, by Egger in the Miocene of Orenburg, and by Speyer 

 in the Eocene of Cassel. 



Cythekopteeon FiPiSTKELLA, nov. sp. (Plate LXIX. figs. 2 a-2 d.) 

 Carapace, as seen from the side, subrhomboidal, with a very large and acutely produced 

 triangular alseform process, which projects below the middle of the ventral margin ; 

 anterior extremity rounded, posterior produced in the middle into a wide truncated 

 beak ; dorsal margin excessively arched, gibbous, highest in the middle ; ventral 

 margin convex, hidden in the middle by the projection of the ventral ala. Seen from 

 above, broadly sagittate, the lateral alse spreading widely, and forming behind the 

 middle of the shell two acute backward-pointing processes, between which and the 

 posterior extremity the margins form a deeply excavated arch ; the extreme width 

 between the apices of the alse is just equal to the length of the shell. End view acutely 

 triangular, the lateral margins nearly straight, ventral margin deeply arched and 

 obscured in the middle by a triangular projection formed by the anterior margin. 

 Surface smooth ; lateral alee channelled and marked by a deep hollow at the base. 

 Length -^ inch (1 millim.). 



This very fine species occurred not uncommonly in the Sables moyens (zone a Bryo- 

 zoaires. 



Genus Bythoctthere, G. O. Sars. 

 Valves subequal, smooth or very sparingly sculptured, almost destitute of hairs ; thin 

 and fragile; hinge-joint quite simple, or composed of a slight bar and furrow; no 

 teeth. Upper antennae elongated, 7-jointed ; second joint large and thick, with a seta 

 on each margin, the other joints much narrower. Lower antennae moderately robust, 

 4-jointed ; second joint large. Mandibles strongly toothed ; palp 4-jointed, with a well- 



