388 Prof. T. Rupert Jones and Br. H. Woodward — 



with any that we can associate with the caudal spines intended. 

 Nor do we find at Ludlow exactly the kind of carapace required. 



To C. leptodactylus Mr. Salter apportioned " a cephalothorax long, 

 triangular, acute in front, broad and rounded behind. Free abdominal 

 segments 7-8 in number, subquadrate, deeply impressed at the sides. 

 Caudal appendages long, striate ; the central spine (telson) scarcely 

 thicker than the long lateral spines. Surface of the head (carapace) 

 smooth, or marked with only very short sparse lines. Abdominal 

 segments strongly striate. The whole animal elongate and more 

 than a foot long." One particular specimen in the Mus. Pract. Greol, 

 is referred to by Mr. Salter at p. 158. We are at a loss here also in 

 fitting the indicated (slender) appendages to the carapace described. 

 We have examined this and other good specimens, labelled C. lepto- 

 dactylus by Mr. Salter or at his direction, in which the carapace 

 agrees with his description. One carapace is of large size, nearly 

 perfect, about 125mm. (5 inches) long, by 55 mm. at greatest height, 

 M. P. G. X i, Catal. Cambr. Sil. Foss. 1878, p. 142. A specimen nearly 

 perfect, M. P. G. x + (Catal. 1878, p. 142), 60 mm. long by 28 mm., 

 gives no certain indication of the length of its telson and its 

 two stylets, for they are crushed off short. The abdomen exposed 

 is about 50 mm. long In specimen D of the Ludlow Museum, which 

 has the proximal portion only of the caudal spines preserved, and in 

 specimen B, with the appendages also broken off short, the telson 

 was ribbed and pitted (=: prickly), thereby differing from the spines 

 known as C. leptodactyhis (M'Coy). 



There is also a well-preserved small specimen (M. P. G. x i, 

 Catal. 1878, p. 142), with its carapace measuring only 25 mm. in 

 length and 11 mm. in height, from the Lower Ludlow of Bow 

 Bridge, Ludlow. This is labelled " C. leptodactyhis," and belongs to 

 the same species as the foregoing. Its caudal appendages are perfect, 

 with the telson (25 mm.) about one-third of the length of the whole 

 animal ; but they differ from M'Coy's C. leptodactylus, for they are 

 not only ribbed or ridged, but the telson was prickly ; the laterals 

 were probably rather more than half its length. Specimen M. P. G. 

 D tf J from Dudley, however, is a thin spiniform fragment, faintly 

 striated like C. leptodactylus. 



Altogether the telson (style) and stylets of these specimens have 

 a very close resemblance to those known as C. MurcJiisoni (see above, 

 ■p. 387). One example, from Dudley, described and figured' as such 

 in the Geol. Mag. Vol. III. p. 204, PI. X. Fig. 8 (stylets and the 

 upper moiety of the style, 90 mm., even more than 5 inches long 

 when perfect), was doubtlessly proportionate to the large carapace, 

 M. P. G. X i, above alluded to, as belonging to an animal more than 

 12 inches long ; the carapace, exposed segments, and the telson being 

 each a third of the whole length. 



Other good specimens of these caudal appendages are : — 



Ludlow Museum, C. Lower Ludlow ; Leintwardine.^ Lower 

 portion of the style and stylets, 130 mm. (5^ inches). 



1 This is mounted with specimen D as one specimen ; but the discrepancy between 

 the two parts is readily seen. It is referred to by the Rev. J. D. La Touche in his 

 Geology of Shropshire, 1884, p. 77. 



