132 ON PERMIAN ENTOMOSTIUCA FROM 



K. Permiana is not uncommon in the shell-limestone of Tun- 

 stall Hill, and in the upper Permian limestone of Byers' Quarry. 



K. Permiana seems to be nearly related to the Eussian species 

 K. (^Cytliere) sticta, Keyserling.* The latter form has rounder 

 extremities, and its ventral margin more deeply sinuate, and it 

 is apparently more compressed than the former. Some differ- 

 ence also exists in the ornamentation, which in K. sticta appears 

 to be very regularly arranged. Both agree, however, in possess- 

 ing two expanded rims on the free margin of each valve. K. 

 Poesslen, Beuss,'|' of the Unter Zechstein, also corresponds in 

 this respect, and will probably prove to be closely related. 



The generic affinities of this species and of its congeners have 

 been until lately involved in some obscurity. When first de- 

 scribed by Mr. Jones, from specimens on the limestone slabs of 

 Byers' Quarry, it was referred by him to the genus Ditliyrocaris 

 of Dr. Scouler. In placing it there, he admitted that it was 

 questionable whether it in reality belonged to that group or not ; 

 for his own specimens were not well preserved, nor had the 

 characters of the genus been properly defined by its author ; but 

 from the data offered by the imperfect materials in his hands, 

 he thought it possible that it might have some affinity to it, 

 and placed it in that genus provisionally. 



Dithyrocaris was originally considered by Dr. Scouler to have 

 a univalve carapace, like Apus and other single-valved Branchi- 

 opoda.\ He afterwards altered his views, supposing it to be 

 bivalve, like Cyjyris, though differing from that genus in having 

 caudal ap^^endages, protruding from the valves. This opinion 

 was held until 1843, when General Portlock described two new 

 species from the slabs of the Lower Carboniferous rocks of Ire- 

 land, and proved that its carapace was univalve, as Dr. Scouler 

 had at first supposed. General Portlock's description of these 

 species, particularly of D. Colei, can leave no doubt of the cor- 

 rectness of his view^ in this respect, and clearly demonstrates 

 that Ditliyrocaris is a univalve Entomostracan — that is, sup- 



* "Loc. cit," p. 112, taf. 4, fig. 38. 

 + " Jahres. Wetterau. Goscll." 1854, p. 70. 



X "Records of Science," Feb. 1S;35; and in a paper read before the British Association at 

 Glasgow. See also Jones on Z)j7/'yror«;/.«, in Professor Kinj,''s " Mon. Pern). Fos8.'"p. 64. 



