306 On the Palceozoic Bivalved Entomostraca. 



10. Bairdia grandis^ Jones and Kiikbj. 

 (PI. XVI. fig. 12.) 



Bairdia grandis, J. & K., Quart. Journ. Geol. Soc. vol. xxxv. 1879, 

 p. 672, pi. xxix. figs. 1 and 2. 



Of B. grandis, as known in Carboniferous strata, there are 

 several finely developed and characteri.stic specimens in this 

 collection, the one figured being one of the best. 



Whether this robust form of Bairdia is exactly the same 

 as the Permian Ostracod described and figured by one of us 

 in 1859 as B. 'plebeia, Reuss, var. grandis, is not quite clear, 

 for the latter is only known to have occurred once, and then 

 in an imperfect condition. There is no doubt, however, as to 

 these Mongolian specimens being the same as the Carbon- 

 iferous Ostracod which we here and elsewhere refer to as 

 B. grandis. They are the same in size, general form, 

 thickness of the shell, and other particulars characteristic of 

 the species. 



B. grandis occurs in the Carboniferous-Limestone series of 

 Scotland, and less rarely in the same series of the north of 

 England. 



11. Bairdia Hisingeri'} (Munster), var. Mongoliensis. 

 (PI. XVI. fig. 13.) 



Bairdia Hisinyeri (Miinster), Jones and Kirkby, Quart. Journ. Geol. 

 Soc. vol. xxxv. 1879, p. 570, pi. xxix. tigs. 4-10. 



Besides the species already noticed there is another form 

 that scarcely agrees with any described Bairdia. It is 

 probably nearest to B. llisingeri, with which, as a variety, 

 we place it at present. It diti'ers from good examples of that 

 species in the dorsal border being straight in the middle and 

 then inclined strongly to the front, also in its longer and more 

 definite anterior and posterior slopes, and in its more rounded 

 anterior extremity. Its carapace is thus highest at the ante- 

 rior third, and its general form is decidedly more elegant 

 than that of B. Ilisingeri proper. We distinguish it as 

 var. Mongoliensis. 



EXPLANATION OF PLATE XVL 



(All the figures are magnified about 25 diameters.) 



ralve. 

 .'ara lace, 

 showing left valve. 

 Fig, 3. Bgthocypris bilobata (Miinster). Carapace, showing right valve. 



Fig. 1. Leperditia Okeni (Miinster). Carapace, showing left vah 

 Fig. 2. Leperditia Okeni (Miinster), var. tnornata (M'Coy). Cf 



