XTPHOCARIS ENSIS. 



II. Genus Xiphocaris, T. B. J. 8f E. W., 1886. 



Cebatiocabis (?), Salter, T. B. J. $■ H. W. 

 Xiphocaeis, T. B. J. 8c H. W. 



Known only by its long, curved, blade-like telson. 



1. Xiphocaeis ensis (Salter), 1860. PL V, figs. 7 a, 7 b, 7 c, 7 d. 



I860. Ceratiocaeis ? ensis, Salter. Ann. Mag. Nab. Hist., ser. 3, vol. v, p. 159. 



1867. — — — In Siluria, 3rd edit., p. 516. 



1877. — — S. Woodward. Catal. Brit. Toss. Crust., p. 71. 



1885. — T. B. J. & H. W. Third Eeport Pal. Phyll., p. 351 j 



G-eol. Mag., 1885, p. 465. 



1886. Xiphocaeis — — Fourth Eeport, p. 233 ; Geol. 



Mag., 1886, p. 460. 



In the Oxford Museum we find the original fossil described by Mr. Salter in 

 1860, namely specimen 0, a large telson (PI. V, fig. 7 a), nearly 6 inches long, 

 lying on its side and flattened, bulbous at its proximal end, sword-shaped, with 

 an incurved apex, a crenato- serrate convex dorsal margin, and nearly flat sides, 

 which have a sub-central rib, giving a lozenge-shaped section (fig. 7 b). Not quite 

 perfect at the point, this telson is 145 mm. long, 16 mm. broad at the bulb, and 

 13 mm. below it. The subcentral line is a low ridge at the top. This is traceable 

 nearer the outside lower down ; and it becomes a central furrow below. Traces 

 of test remain here and there. Both edges are minutely serrated (figs. 7 c and 

 7 d). Along and close to the inner (concave) edge there is a multiple row of pits 

 (the bases of the small spines or prickles), in threes and fours, obliquely set along 

 the upper half, below the bulbous portion ; and these are feebler and fewer lower 

 down, and die out downwards in a less regular, thinner, and more scattered series, 

 until they become an irregular row of single pits. Coarsely granular, radiating, 

 and other markings, due to casts of parasitic Polyzoa, cover the bulb and occur 

 here and there on the spine itself. The lowest portion is smooth. 



The arrangement of the pitting along the concave edge may by itself indicate 

 a distinct generic relationship. It reminds us of Barrande's C. debilis, as figured 

 in his ' Sil. Syst. Boheme,' vol. i, Suppl. pi. 18, figs. 26—28, and pi. 31, fig. 16— 

 19. Altogether its large size, its curvature, and the serration on both the upper 

 and the lower edge, and the profuse spination (as shown by pits) on the latter 



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