BRITISH FOSSILS. 101 



Of the intermediate rings we have very few fragments, but several 

 hinder rings, which must have been near to the extremity both from 

 their form and their being quite covered with the elongate tuber- 

 cular plicae. 



Plate IX. fig. 7, from the cabinet of Mr. Marston, represents 

 probably the penultimate ring. It is two inches and a quarter long 

 by two inches at its truncated extremity, which is rather wider than 

 its base. The shape is thus nearly square, the sides are but very 

 slightly (perhaps not at all) curved, nor is the base a contracted or 

 the distal end 6 expanded or produced, as in P. anglicus. The edge 

 is crenate. Plate XIII. fig. 5 is from the Upper Ludlow Rock. 



The caudal joint (telson) is yet wanting and should be sought 

 for, as in all probability it was not unlike that figured on Plate VIII. 

 fig. 1 1 has possibly something to do with it. 



Mr. J. Harley, of King's College, has found a small specimen, 

 doubtless of this species (Woodcut, fig. 14), since the plate was 

 finished. It has the second to the sixth rings united, and the 

 pyramidal form of the front ring is very marked. 



Fm - 14 ' From Lower Ludlow 



Anterior body rings of U~ > R oc k, Leintwardine. 



Pterygotus punctatus. I In the collection of 



The first segment (____ ^=z== === ==--_ J Mr. J. Harley. 



lost. 



Appendages. 



Antenna;. Of these great pincer-like organs only two chelae have 

 been found, one three inches and a half long, but these are quite 

 different in proportion from that of P. anglicus. The shaft is much 

 longer and slenderer, being quite eight times as long as wide, and 

 not much thicker at the origin than near the tip. The teeth are 

 much shorter, the central one is as long as the diameter of the chela 

 itself, and placed beyond the middle ; two other primaries nearly 

 equal in size and a secondary tooth are outside it, while only minute 

 teeth with a single primary near the hinge occur on the proximal 

 half. As many as twenty of these small conical teeth may be 

 counted in the inner half, and eleven or twelve on the outer. The 

 primaries are broad-conical (not ovate), striated and directed back- 



