130 ON PERMIAN ENTOMOSTRACA FROM 



Aiitenor exti^emity angulate at its junction with the dorsal 

 margin, and bluntly rounded ventrally : the dorsal angle 

 is sometimes the most prominent ; at others a point mid- 

 way between the margins protrudes most. Posterior ex- 

 tremity angulate dorsally, more pointed than the former, 

 the antero-dorsal angle being more projecting, from which 

 a convex line slopes gradually to the ventral margin. 

 From the extreme points of the dorsal margin of each 

 valve proceed two strongly produced rims, or marginal 

 expansions, which become more widely separate as they 

 approach the ventral margin. The innermost rim (of single 

 valve) is elevated, and forms a raised reflexed edge round 

 the middle portion of the valve. The outermost^ or most 

 ventral rim, is not reflexed, but projects at a right angle 

 from the ventral portion of the valve ; along the inner 

 surface of this rim, which forms the contact margin of 

 the valve, extends a slightly elevated projection, on. a 

 plane with the ventral convexity of the valve, and which 

 appears to overlap a similar longitudinal projection in the 

 opposite valve. The outer surface of the valve within 

 the innermost rim is deeply channelled. The central area 

 of the valves is protuberant, rising abruptly from the 

 channelled depression just mentioned ; dorsally, and to- 

 wards the posterior extremity, this area is very promi- 

 nent, or slightly gibbose. Surface ornamented with a 

 network of slightly raised, irregularly hexagonal meshes 

 bounding shallow pits, and with slender longitudinal 

 wrinkles (formed when the network has a parallel arrange- 

 ment of its meshes), which occasionally bifurcate and 

 merge into each other Hinge consisting of the dorsal 

 margins, united by ligament (?) Lateral contour ovate, 

 with strongly produced extremities. 



This remarkable species does not vary much in marginal out- 

 line. The posterior extremity is occasionally rather less pointed 

 than usual, and the anterior extremity varies a little in convexity ; 

 the ventral margin also has at times a tendency to become sinuate. 



