from the Silurian Rocks. 157 



projecting', anterior mucro. The striation is coarse. We have 

 not found the body-rings; but a fragment of the telson from 

 Kendal shows a ribbed surface. 



Locality. Benson Knot, Kendal, in Upper Ludlow rock. 



C. ellipticus, M'Coy, /. c. pi. 1. fig. 8, appears to be only an 

 incomplete specimen of C. inornatus, but probably of a distinct 

 variety. It has all the angles rounded off, or, as I believe, 

 partly concealed in the stone. It is from the same locality. 



4. C. Murchisoni, M'Coy, sp. 



Figured as a fish-defence (Onchus Murchisoni) in the ( Silurian 

 System/ 1839, pi. 4. figs. 10, 64*, and described as part of Ptery- 

 gotus (Leptocheles) leptodactylus, M f Coy, Synops. Woodw. Foss. 

 p. 176. Ceratiocaris Murchisoni, ( Siluria/ 2nd ed. pi. 19. fig. 1, 

 p. 263. 



C. modicus. Cephalothorax biuncialis, oblongus, convexus, lineis 

 remotis interrupts subrectis ornatus. Abdomen segmento ultimo 

 perstriato. Appendices caudales longse, subcylindricse, centralis 

 (telson) ad basin bulbosa costaque dorsali percurrente valida ; 

 laterales longse ; omnes costatae. 



Of this, the first- discovered species, only numerous fragments 

 are known. Its telson was figured, as above noted, for a fish- 

 defence ; and it is indeed difficult, without the microscope, to 

 decide whether some of the hollow spines found in the uppermost 

 Silurian beds be those of Crustacea or Fish. This, however, 

 is quite a clear case. It was determined to be Crustacean by 

 Prof. M'Coy in a paper full of acute observation, published by 

 him in the ' Quarterly Geol. Journal/ vol. ix. p. 12. He, how- 

 ever, thought it to be the long didactyle claw of one of the 

 Pterygoti, which he considered closely related to Limulus. 



Locality. Only in the Upper Ludlow rock and Downton 

 Sandstone, near Ludlow; specimens are in the collections of the 

 Ludlow geologists, and in the Museum of Practical Geology. 



5. C. leptodactylus, M'Coy, sp. 



Pterygotus (Leptocheles} leptodactylus, M'Coy, Syn. Woodw. 

 Foss. pi. 1 E. figs. 7,7a,7b (not c, d). 



C. pedalis et ultra, elongatus. Cephalothorax longus triangulatus, 

 antice acutus, postice valde rotundatus, latus. Segmenta libera 

 7-8? subquadrata, lateribus profunde impressa. Appendices 

 longse striatse, centralis (telson) lateralibus longis vix crassior. 

 Superficies capitis laevis, nisi lineis brevissimis sparsis notata, 

 segmentorum perstriata. 



This is of quite a distinct type from those before described, 

 * Fig. 63 may be a portion of another species : it is strongly keeled. 



