270 Prof. T. R. Jones on the 



imitate P. Smithii (Ann. & Mag. Nat. Hist. I. c. pi. iv. 

 fig. 5) to some extent, but still being much more attenuate 

 and subacute at the ends, although the median convexity is 

 strong. 



III. Bythocypeis, G. S. Brady, 1880. 

 (Ann. & Mag. Nat. Hist. Marcli 1887, p. 184.) 



1. Bytliocypris HoUti^ Jones, var. ohlonga, no v. 

 (PI. XV. tigs. 1«, h, c.) 



Proportions :— L. 25. H. 14. Th. 13. 



This is rather more oblong in side view than the published 

 type * and also more compressed. 



B. Hollii has been found also in the Frojel shale, Goth- 

 laud. 



2. Bjitlwcypris caudalis, sp. nov. 

 (PI. XV, figs. 2 a, Z», c, and 3 a, b, c.) 



Proportions : — < y'^^ 



In both the figured specimens the postero-dorsal region 

 slopes more rapidly than in B. Hollii and ends with a blunt 

 projecting angle, with which the hinder ends of the valves, being, 

 as it were, squeezed or pinched together, form a kind of caudal 

 process. The antero-dorsal edge also slopes down with a 

 lower curve than in B. Holliiy giving a subovate outline to 

 the valves. 



Fig. 2 a, however, has a bolder and more uniform curve on 

 its postero-dorsal slope than shown in fig. 3 a, where the 

 posterior constriction is more strongly marked; this latter 

 variety, too, is shorter, higher in proportion to its length, and 

 has a somewhat fuller ventral curve. In edge view (figs. 2 h 

 and 3 h) and in end view (figs. 2 c and 3 c) there is no specific 

 difference. 



3. Bythocypris symmetrica^ Jones, var. ohesa, nov. 

 (PL XV. figs. 7 a, h, c.) 



Proportions :— L. 17. H. 9. Th. 9. 



This carapace is very much like that of B. symmetrica, 

 var. h (Ann. & Mag. Nat. Hist. /. c. p. 186, pi. vii. fig. 4), 

 * Op. cit. p. 184, pi. V. figs. 1 and 2, and pi. vi. figs. 3 and 4. 



