336 REPORT—1885. 
1882. Ceratiocaris, B. N. Peach. ‘Trans. R. Soc. Edinb.’ vol. xxx. part 1, p. 73. « 
1883. Ceratiocaris, A. S. Packard, jun. ‘Monogr. North-Amer. Phyllop. Crust.’ : 
‘Twelfth Ann. Rep. U. 8. Geol, and Geograph. Survey,’ p. 450. ; 
1884. Ceratiocaris, C. E. Beecher. cs Enea Upper-Devon. Measures’; ‘ Second’ 
Geol. Surv. Penns. P.P.P.’ p. 2 
1885. Ceratiocaris, O. Novak. ‘§ Sitzungsb. k. béhm. Gesellsch. Wissensch.’ 
1883. Ceratiocaris, H. W.and T. R. J. * Report Brit. Assoc.’ for 1883, p. 217, 
1884. Ceratiocaris, T. R.J.and H.W. ‘Geol, Mag.’ Dec. 3, vol. i. p. 396. 
A. British Species. 
1, Ceratiocaris Murcutsoni (Agassiz), and its variety LEPTODACTYLUS 
(M‘Coy). 
Some imperfect caudal appendages or spines (telson or style, and 
lateral spines or stylets), from the Uppermost Ludlow strata, near 
Ludlow, were figured in Murchison’s ‘ Silurian System,’ in 1839, as fish- 
defences. These were recognised by Prof. F. M‘Coy in 1853 as being 
very similar to some analogous fossils, referred by him at first (in 1849) 
to a slender-clawed kind of Pterygotus from the Lower Ludlow, at 
Leintwardine, near Ludlow, which he separated from that genus as 
Leptocheles leptodactylus. M‘Coy suggested that Murchison’s fossil 
should be known as L. Murchisoni.! 
In each case we have only caudal spines to deal with; but M‘Coy’s 
specimens (‘ Brit. Pal. Foss.’ pl. 1 E, figs. 7, 7a, 7b) are much more slender 
than Murchison’s (‘Sil. Syst.’ pl. 4, figs. 10 and 64, and ‘ Siluria,’ pl. 19, 
figs. 1, 2), and less strongly ribbed ; and therein they seem at first sight 
to have specific differences. 
Several good examples of more or less perfect sets of the three caudal 
spines corresponding in size, strength, and ribbing with Murchison’s 
fossils have been met with. These show evidence of lines of prickles (by 
the presence of little pits, representing their bases, along one or more 
lines); and on close examination the engravings in the ‘ Sil. Syst.’ and 
‘ Siluria’ (the specimens have been lost) show some slight indications 
of this spinose ornament. This is not visible, however, in M‘Coy’s 
figures or specimens (Cambridge Museum, a /925, a/924). Of these latter, 
more delicate, caudal appendages, very few other examples occur. R 
In the collocation of these caudal appendages with their respective 
carapaces we have some doubt and difficulty. 
We have not found a carapace directly associated with any complete 
spines of either the Murchisuni or leptodactylus type except in the case of 
a very small specimen (M. P. G. x +), which appears to have the caudal 
appendages of C. Murchisoni and the carapace of Salter’s ‘ leptodactylus.” 
With regard to both, however, the late Mr. J. W. Salter satisfied himself 
that he knew their special carapaces, for he described them at p. 157 
of the ‘ Ann. Mag. Nat. Hist.’ for March 1860: where also he refers both 
species to the Ceratiocaris of M‘Coy. Judging from his Latin diagnoses, 
he allocates to the former—‘ a cephalothorax (carapace) two inches long, 
oblong, convex, ornamented with interrupted, nearly-straight, wide-apart 
lines. The caudal appendages long, aie ania the central spine 
1 Prof. M‘Coy’s observations are as follows :-— . As before mentioned, figs. 9, 
10, and 11 [Si/. Syst. pl. 4; omit figs. 9 and 11], ‘veut the so-called Onchus 
Murchisoni, Ag., are almost identical in form, size, sculpturing, and all other — 
characters (as far as they are represented in these drawings), with the distinctly 
didactyle pincers which I have figured (Brit. Pal. Foss. pl. E, fig. 7) from Leintwar- — 
dine, under the name Lept. leptodactylus. . . . If this approximation prove correct, — 
the fossil should in future be called Leptocheles Murchisoni (Ag. sp.).—@Q. J. @. 8. 
vol. ix. 1853, p. 13, 
cyt 
