Palceozoic Bivalved Entomostraca. 269 



to Bythocypris Phillipsiana ; but the overlapping valve is 

 the right instead of the left. The dorsal edge is elliptically 

 arched, the ventral nearly straight, and tlie ends are neatly 

 rounded, with one of them smaller than the other. 



Macrocypris Vinei, Jones, is also found in an Upper- 

 Silurian (Wenlock) shale at Frojel in Gothland. Ann. & 

 Mag. Nat. Hist. June 1888, p. 396. 



II. PoNTOCYPRis, G. O. Sars, 1865. 



(Ann. & Mag. Nat. Hist. March 1887, p. 182.) 



There appear to be three varieties of Pontocypris Mawii *, 

 Jones, in the Silurian clay of Wisby. 



1. Pontocypris Mawii^ Jones, var. hreviata, nov. 

 (PL XV. fig.s. 4 a, 5, c.) 



Proportions :— L. 20. H. 11. Th. 8. 



Shorter and rather thicker than the published type, but 

 still somewhat compressed ; hence appearing in side view 

 irregularly subovate, like an orange-pip. It approaches very 

 nearly in outline to the figure of the thick variety of P. 

 Mawii '\ irova Frojel (Wenlock shale), Gothland; but it is 

 too high and blunt anteriorly and is much less convex on the 

 sides. Its hinder extremity is slightly pinched, but not nearly 

 so much as in Bythocypris caudalis (figs. 2 and 8). 



2. Pontocypris Mavni, Jones, var. proxima, nov. 

 (PL XV. figs. 5 a, h.) 



Proportions:— L. 21. H. 10. Th. 9^ 



This is very similar to the type, but is proportionally 

 thicker, that is, more convex, though still retaining a slight 

 flattening on the sides (faces) of the valves, and the anterior 

 slope is less steep. 



3. Pontocypris Mawii ^ Jones, var. divergens^ nov. 

 (PL XV. figs. Qa,h,c.) 



Proportions :—L. 23. H. 11. Th. 10. 



The carapace is here lengthened proportionally, the pos- 

 terior moiety being contracted above and below, so as to 



• Op. cif. pp. 182, 188, pi. iv. figs. 4, 6, and 7. 



t Ann. & Mag. Nat. Ilist. ser. 6, vol. i. p. 397, pi. xxii. fig. 3. 



