BRITISH FOSSILS. 15 



short, enlarged, and swollen, is produced into a long slender process, 

 pointed and incurved at its extremity, and beset with very strong 

 and numerous, unequal, striated teeth. The third joint is articulated 

 with the enlarged basal part of the second, so that its similarly 

 incurved extremity is opposable, like a thumb, to the latter. It 

 possesses teeth of a similar structure to those in the other ramus of 

 the chela, and opposed to them as the canine teeth in the upper jaw 

 of a mammal are opposed to those in the lower, passing, that is, 

 behind the others, or on their proximal side. 



(6.) The second kind of appendage (Plate VII. figs. 4, 5, 6, 7,) 

 presents a large flattened basal joint, produced at one extremity, 

 and truncated obliquely to its long axis at the other. The 

 truncated margin is slightly curved, and is beset with long and 

 strong, curved and pointed teeth, which are longer at one end of 

 the series than at the other ; and are so constricted at their bases, 

 as to appear to be articulated with the basal joint. 



Of the two longest margins of the latter, the one has a general 

 convexity, while the other is concave. The outer part of the former 

 exhibits a sort of notch or step, in which is lodged the basal joint 

 of a long palpiform appendage. This joint (c) is very short and 

 somewhat swollen. 



The next articulation (&, longer and subcylindrical, is broader dis- 

 tally than proximally. The third e), twice as long as the last, has 

 a nearly equal breadth throughout. It is exhibited in situ, and in 

 its whole length, by only one specimen (Plate VII. fig. 4), and here 

 the distal extremity is rounded and slightly emarginate. 



In the same specimen (and only in this) a fourth joint (/) may be 

 observed. It is as long as the third, but of a different form, the 

 distal end being much wider than the rod-like proximal extremity. 

 The internal edge of the distal extremity is rounded and slightly 

 serrated, and is apparently the natural edge of the part ; but there 

 are appearances which lead one to suspect that the continuation of 

 the outer angle has been broken away. 



The characteristic sculpture is visible upon the surface of the 

 basal joint of this appendage, more particularly towards the anterior 

 edge of its inner region, and the convexities of the facets are here 

 directed towards the convex long margin. The outer wall of its 

 outer region in fig. 4 is broken away, and the matrix contained in 

 the interior has become detached, so as to show the inner surface of 

 the opposite wall, which is perfectly smooth. 



In the recent state a considerable interval, doubtless filled by 

 muscular and tendinous soft parts, must have existed between the 



