154 ON PERMIAN ENTOMOSTRACA FROM 



By carefully looking for the distinctions above-mentioned, I 

 believe that many of the Bairdm of palaeontologists will be 

 fonnd to belong to Cytherideis. 



The animal of Cytherideis (as far as yet studied) appears to be 

 truly a Cythere. 



The form referred by Dr. Eeuss (" Jahres. Wetter. Ges. 

 1854," p. 65, fig. 3, and possibly fig. 2), to Bairdia gracilis^ 

 M'Coy, seems to me (as already indicated also by Mr. Kirkby) 

 to be a narrow variety of the species here termed C. Jonesiana. 

 I believe that M' Coy's B. gracilis (though I have not yet seen 

 the specimen) is a true Bairdia; Dr. Richter's specimen of B. 

 gracilis (" Zeitsch. Geol. Gesell.," vol. vii., p. 530, pi. 26, figs. 

 16, 17) also appears to be a Baiixlia; and I may say the same 

 of the very imperfect specimen from Byers' Quarry, indicated in 

 the " Monog. Perm. Foss.," pi. 18, fig. 7. 



Cythere bub-reniformis,* Kirhhy. PI. IX., fig. 13. 



Bairdia renifoiinis, Kirkby. " Ann. Nat. His.," 3rd 

 ser., vol. ii., p. 329, pi. X., fig. 13. 

 Length, l-35th of an inch; height, l-75th of an inch. 

 Carapace sub-reniform, flatly convex, obtuse marginally, 

 smooth; dorsal margin almost straight centrally, but 

 slightly inclined towards the anterior extremity ; antero- 

 dorsal region convex, sloping quickly to anterior extremity ; 

 postero-dorsal region convex, abruptly falling two-thirds 

 of height; ventral margin convex towards extremities, 

 with a rather deep sinus anteriorly situate; anterior ex- 

 tremity rounded; posterior extremity obtusely pointed; la- 

 teral contour sub-lenticular, compressed, convex towards 

 the extremities, more so posteriorly than anteriorly; 

 greatest diameter central, rather more than one-fourth of 

 length; hinge with left dorsal margin moderately over- 

 lapping the right. 

 C. sub-reniformis has some resemblance to Bairdia Schauro- 

 thiana. It is distinguishable, however, by its more Cythere-like 



* The term reniformis being pre-occupicd, I have changed the specific name of this 

 species to sub-yen if onnis. 



