436 Mr. J. W. Kirkby on Permian Entomostraca. 



aspect : this is particularly the case in young specimens. The 

 postero-dorsal region of this area is always the most prominent 

 portion of the valve ; and as the central portion of the dorsal 

 region is at times rather depressed, both it and the antero-dorsal 

 angle have then a gibbose appearance. Such specimens assimi- 

 late to the L. (Cythere) Schrenkii* of Keyserling, whose equi- 

 valent regions are extremely gibbose. As the central area varies 

 in prominence in different specimens, so do specimens vary in 

 width, and that very considerably. 



Although there can be little doubt of this species being cha- 

 racterized by a punctured surface, yet it is a character that has 

 only been observed in two specimens, both of which are repre- 

 sented in PL XI. Usually the surface is either smooth, like that 

 of fig. 5, or wrinkled, like that of fig. 8, and shows no traces of 

 punctures, even when viewed with the aid of a high magnifying 

 power. Perhaps this may result from a peculiarity of fossiliza- 

 tion, though, from the number of specimens which have been 

 examined, it is more likely that some individuals of the species 

 were punctured and others were not. The punctures which 

 have been detected are minute, and require a lens of moderately 

 high power to resolve them. They are observed best on the 

 central and dorsal areas ; indeed I have not noticed them else- 

 where. The longitudinal wrinkles are also confined to the same 

 regions, but chiefly to the central area. They are tenuous, and 

 trend somewhat irregularly in a direction parallel with the free 

 margins. 



L.t Permiana seems to be nearly related to the Russian spe- 

 cies, L.I stricta, Keyserling f. The latter species has rounder 

 extremities, its ventral margin more deeply sinuate, and is ap- 

 parently more compressed than the former. Some difference 

 also exists in the punctured ornamentation, which in L. stricta 

 is very regularly arranged. Both agree, however, in possessing 

 two expanded rims on the free margin of each valve. L.I Roess- 

 lerij ReussJ, of the Lower Zechstein also corresponds in this 

 respect, and will probably prove to be closely related. 



It is not uncommon in the fossiliferous limestone of Tunstall 

 Hill, and in the Upper Permians of ByeiV Quarry. 



The generic affinities of this species and of its congeners are 

 involved in some obscurity. When first described by Mr. Jones, 

 from specimens on the limestone slabs of Byers' Quarry, it was 

 referred by him to the genus Dithyrocaris 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 



* Reise durch die Tundren der Samojeden, p. 112. taf. 4. fig. 37. 



t Loc. cit. p. 112. taf. 4. fig. 38. 



X Jahres. Wetterau. Gesell. 1851-1853, p. 70. 



