66 BRITISH PALEOZOIC PHYLLOCARIDA. 



distinguish our fossil from other telsons ; and more particularly its lozenge-shaped 

 sectional area of an unequal rhombic form, blunter at the outer (upper) and 

 convex edge than on the other, the ridge along the sides not being quite on the 

 medial line, but nearer the outer than the inner edge. Neither the carapace 

 nor the stylets of this species are known as yet. We have proposed the name 

 Xiphocakis 1 for this rare genus. 



M. Barrande's Ceratiocaris primula (see our ' Third Report,' p. 357) has a 

 style (or stylet ?) with lozenge- or diamond-shaped section ; but, though curved, 

 it is of different dimensions and is pitted all over. 



PI. V, fig. 7. Oxford Museum (Grindrod Collection). Collected by Mr. A. 

 Marston ; marked " Cerat. ensis ;" from the Lower Ludlow series at Leintwardine, 

 Shropshire, according to Mr. Salter (' Ann. Mag.,' I. c). 



In hard, grey, micaceous mudstone, with a few small, obscure, organic markings ; 

 calcareous at the edge. 



There is another similar but much less distinct specimen of Xiph. ensis in the 

 Oxford collection, from near Ludlow. 



III. Genus Physocaris, Salter, 1860. 



Ceeatiocaeis, Salter. 



Phtsocaeis, Salter, T. B. J. Sf H. W. 



Known only by a unique specimen of an orbicular, probably bladder-like, small, 

 thin carapace, with its abdomen and caudal appendages. 



1. Physocaris vesica, Salter, 1860. PI. VII, figs. 8 a, 8 b. 



I860. Ceeatiocaeis (Phtsocaeis) vesica, Salter. Ann. Mag. Nat. Hist., ser. 3. 



vol. v, p. 159, woodcut fig. 

 1865. — — — Salter & H. Woodward. Chart Foss. 



Crust., p. 17, fig. 8. 

 1865. — — — Huxley S{ Etheridge. Catal. Foss # 



M. P. G., p. 79- 

 1867. — vesica, Salter. In Siluria, 3rd (4th) edit., p. 517. 



1877. (Phtsocaeis) vesica, H Woodward. Cat. Brit. Foss. Crust., 



p. 72. 



1878. vesica, Huxley, Newton, Sf Etk. Cat. Foss. M. P. G., p. 142. 

 1884. — — LaTouche. Handbook Geol. Shropsh., pi. 22, fig. 816. 



1 zifo$, a sword ; Kapis, a shrimp. 



