Osiracodous and Phyllopodous Ti-ihes. 73 



Liljeborg; 4. Bradycinetus, Sars; 5. Eurypylus, Brady. The 

 nearly related Conchoecia, Dana, and Halocypris, Dana, constitute 

 the Conchoeciadm. Heterodesmus is a distinct form allied to the 

 Cypridinada. Polycope is the type of a different family ; and 

 Cytherella is the type of another. 



In the fossil state the valves alone remain for our examination ; 

 and however similar they may appear to those of this or that genus, 

 doubt must always be entertained as to the relationship of the 

 animal to existing forms ; for it may have exhibited a very different 

 construction of other parts of the frame. Yet the fossil forms 

 must be placed in some kind of category ; and in preference to a 

 purely artificial arrangement of all the fossil forms of Cypridinadse 

 and their immediate alhes under such a provisional genus as " Cypri- 

 dinopsis." I venture to express such evidence of their relationship 

 to existing forms as is recognizable, by placing them in the existing 

 genera, or under genera supposed to be in alliance with them, as 

 already planned by De Koninck and others. 



Among the fossil, subglobose, ovate-oblong, anteriorly notched, 

 bivalved Entomostraca, we find some with oval outline, distinctly 

 notched, at the middle of the front end, by a sinus, with a projecting 

 or hooked peak. Although the valves are thicker than those of the 

 existing true Cypridinae, and though the lost soft parts probably 

 differed somewhat, these forms are placed under that genus for the 

 sake of convenience, thus serving palaeontological purposes and 

 avoiding multiplication of terms. As an example of this group, 

 Cypridina Phillipsiana is figured in PI. LXL, Fig. 8, vol. iv., with 

 its long shallow sinus and small beak, and its large radiate muscle- 

 spot. We know of twelve other species from the Carboniferous strata 

 of the British Islands, including Cypridina primseva {Baphnia, 

 M' (7.), which closely approximates in shape to the existing C. norvegica 

 and others of a nearly oval outline. C. radiata, from the Scotch 

 and English Coal-measures, also oval in profile, has peculiar star-like 

 vascular patches in its valve-structure. Its real outer surface has a 

 small but coarse blebby reticulation ; the convex tops of these bladder- 

 like meshes rub off, and leave irregular hexagonal raised lines. 

 This surface flakes off, and exposes the radiate inner structure of 

 the shell. 



Another group of allies are also notched and beaked in front, but 

 are subovate in profile and acuminate behind ; moreover, the lower 

 part of the front margin has a tendency to be exaggerated, or pro- 

 duced like the prow of an ancient trireme, or a modern armour-clad 

 " Piam " or " Monitor." In the oblong Cypridina above mentioned 

 this antero-ventral margin was liable to decrease, so that in G. 

 hrevimentum, common in the Mountain Limestone, the strong beak 

 stands out from a chinless front. And in another group the chin 

 is altogether wanting, and the antero-dorsal angle projects as an im- 



