190 Mr. G. S. Brady on undescrihed Fossil Entomostraca. 



covered with conspicuous concentrically arranged pits, v/hich 



are well developed towards the margins, but nearly obsolete 



at the centre of the valves. Length -^Vth of an inch. 



This species is either identical with, or very closely related to, 



a recent form which is common in deep water on many parts 



of the British coast, but which appears hitherto to have escaped 



description. 



Cythere arborescens, n. sp. PI. IX. figs. 5-8. 



Carapace broadly oval, well rounded in front, about once and a 

 half as long as broad. The left valve is much larger than the 

 right, overlapping it considerably on the dorsal and posterior 

 margins. Tiie dorsal margin is strongly arched, and slopes 

 somewhat steeply behind towards the ventral margin, the two 

 being produced at their junction into an obtusely angular 

 prominence. Ventral margin nearly straight, somewhat in- 

 curved at its anterior third, and sloping gently upwards be- 

 hind. The dorsal outline is oblong oval, compressed. End 

 view ovate. iSurface of the shell finely punctate, marked at 

 the extremities and along the ventral margin with an elevated 

 reticulated pattern, the ramifications of which are gradually 

 lost on the surface of the valves. Length -rjVth of an inch. 

 The recent species Cythere convexa differs from the present 

 only in the general outline of the valves, which in C. arbores- 

 cens are more decidedly quadrangular, and in the ornamentation 

 of the surface. But though there is much diversity in the sculp- 

 turing of C. convexa, I have never met with any specimens, either 

 recent or fossil, which show the least trace of the beautiful ar- 

 borescent ribbing characteristic of the present species. The 

 surface is also more finely punctate than in C. convexa ; but I 

 should not, on this account alone, have thought it justifiable 

 to propose for it a distinct specific name. 



Cythere aspera, n. sp. PI. IX. figs, 12-19. 



Valves oblong, quadrilateral, compressed. Extremities nearly 

 equal, the anterior obliquely rounded, bordered by an elevated 

 nodulated ridge, which terminates in a conspicuous tubercle 

 over the anterior hinge, and is fringed with short blunt spines. 

 Posterior border produced into a broad flattened lamina, which 

 bears at the ventral angle three or four strong squamous 

 spines. Dorsal margin nearly straight ; ventral sinuated and 

 squamous behind. Seen from above, the carapace is com- 

 pressed, oblongo-ovate, tuberculated, spinous behind. End 

 view quadrilateral. Surface of the valves marked by three 

 conspicuous longitudinal ridges, the ventral ridge sharply 



