Fahcogoic Bivalved Entomostraca. 183 



thicker and higher end being the anterior is proved in recent 

 specimens by the position of internal organs. The valves 

 are smooth and subtriangular ; the left overlaps the other 

 on the dorsal border, and the right valve overlaps on the 

 ventral border. The lateral contour (seen in the edge view) 

 is subovate, with rather flattened sides and subacute ends ; 

 but these features differ with individuals. The shape differs 

 from long- to short-pjriforai (figs. 4 and 6). Thus, still 

 keeping their differences within bounds, the valves are much 

 longer in figs. 4 and 7 than in fig. 6 (var. gibhera). The 

 differences between the short and hump-backed variety (fig. 6) 

 and the long pear-shaped form (figs. 4 and 7) are striking, 

 but not sufficient to make them specifically distinct. They 

 may be sexual differences : the valves were probably thin in 

 substance. 



G. S. Brady's figure of Pontocyjrris faha (Reuss), " Report 

 Ostrac. ' Challenger,' " pi. i. fig. 4, comes near to our Silu- 

 rian form ; but this latter seems to be distinct from any, and 

 requires a name. I propose to name it P. Maioii, dedicating 

 it to Mr. George Maw, F.G.S., who so thoughtfully had 

 some tons of the Silurian shales near Benthall, in Shropshire, 

 thoroughly washed and sifted, and instigated his pala3onto- 

 logical friends to submit the sorted contents to scientific 

 examination. 



There is much resemblance between the Lower-Silurian 

 Cythere Jnkesiana^ J. & H , Ann. & Mag. Nat. Hist.'ser. 4, 

 vol. ii. p. 57, pi. vii. fig. 6 (misprinted " fig. 7," ibid. p. 62), 

 and some of the specimens before us. The former, however, 

 has a more ta];)ering posterior moiety (regarded as '' anterior," 

 loc. cit.), and less of the dorsal convexity. It is advisable to 

 refer the above-mentioned Kildare specimen to Pontocypris. 



VineColl.no. V. (fig. 6). Bedno.22. Build- 

 was Beds. 



VI. Bed no. 25. Tickwood 

 Beds. 



VII. (figs. 4 and 7). Bed no. 22. 

 Buildwas Beds. 



IX. Bed no. 25. Tickwood 

 Beds. 

 LXiv,^, j„ jg. Buildwas Beds. 



Ten specimens : — Smitli CoU. no. 56. Eailway-cutting, side 



of Severn, Iron bridge. 



Twenty-seven 

 specimens : ' 



