PalcBozoic Btvalved Entomosfraca. 413 



3. j^chmina depressicornis, sp. nov. 

 (PI. Xlir. figs. 7 a, 7 b, 7 c.) 



Proportions : — 



Thickness at root Length of Width between 

 Length. Height. of spikes. spike. the tips. 



llf 5i 4 5 11 



The carapace in this species is small and relatively longer, 

 narrower, and thinner than the foregoing, the antero-ventral 

 margin having less convexity even than we see in fig. 4 a, 

 and the valves being rather, less convex. The characteristic 

 Bpikes or horns are placed as usual, but protrude almost 

 horizontally (fig. 7 b) , having a relatively lower angle of 

 divergence, namely (1) from the top of the valves 10°, (2) 

 from the middle of the front 30°. 



The end view (fig. 7 b), though still reminding us of bovine 

 horns, cannot be safely matched with those of any special 

 animal; it is almost like a three-rayed "Star. 



4. jEchmina hrevicornis, sp. nov. 

 (PL XIII. figs. 8 «, 8 b.) 



Proportions : — 



Thickness (including Width be- 



the root of the Length of tween the 



Length. Height. spikes). spike. tips. 



25 16 11 3 6 



This rather rare form has proportionally a greater height 

 of valve than ^ch. cuspidata, being much shorter, and is 

 actually higher than ^ch. bovina, which it most closely 

 resembles in the nearly semicircular outline of the ventral 

 margin. The hollow process on the dorsal region is very 

 short and feebly developed, the surface of the valve not being 

 carried outwards so much as in the other species ; and the cara- 

 pace is therefore relatively thinner than the others. 



The end view of this short-horned species is somewhat 

 sagittate, with the barbed extremity upwards ; or it might be 

 described" as a narrow acute-oval, with a triangular piece 

 removed from the top. 



VIII. Appendix. 



The number of Specimens. 



With the view of indicating api)roximately the numerical 

 value of each species of the Silurian Ostracoda as described in 

 Ann, (& Mag. N. Hist. Ser. 5. Vol. xix. 29 



