BRITISH FOSSILS. 41 



The caudal joint (telson) is only two-thirds as wide as long, and 

 nearly double the length of the penultimate one. It is rather wider 

 behind, and strongly emarginate ; a deep furrow takes its origin, 

 from the notch, and continues more than half way up. There 

 is a low keel at the upper end joining that of the preceding segment, 

 but only for a very short distance. 



The outer margins of the body and tail segments appear to be 

 quite smooth, not serrate or crenate as in several other species. 



The thickness or rotundity of the joints we have no means of 

 ascertaining. 



The sculpture is minute and characteristic, but is only visible at 

 a few points. None has been observed on the head. On the body 

 joints numerous small semicircular plicae (fig. 2 a) the curve open 

 forwards cover the surface, but are less conspicuous on the hinder 

 portions of each segment. On the anterior narrow segment they 

 are perhaps most prominent, and on this and some other of the 

 front rings a raised transverse thread-like ridge runs across at 

 about the middle, or a little in advance of it, but does not limit 

 the conspicuous portion of the sculpture. 



Under Side of Head, and Appendages. 



In three or four specimens, figs. 1, 3, 4, 9, &c. the organs of the 

 mouth, with the antennae, are in situ, and in others the appen- 

 dages of the head occur so grouped together as to show that they 

 were associated. Fig. 3 appears to have the parts most complete. 



Antennae (fig. 6, &c.) None have been found more than two 

 inches long by a quarter of an inch broad at the base of the chelae, 

 the free joint of which is, in antennae of this size, about six-tenths of 

 an inch long. The base of the fixed finger is but slender, scarcely 

 thicker than the preceding joint, and is shorter than the chelre, the 

 shafts of which are linear and straight. (Fig. 7 is broader than usual, 

 and may indicate a difference of sex.) The points of the chelae 

 are sharply incurved ; their armature is minute, of small and larger 

 teeth. 



There are apparently but four joints in the antennae, the basal 

 one small, the second, fig. 7 6 (both figs. 6 and 7 are wrongly drawn 

 as to the length of the lower joints, from being so much broken), at 

 least five times as long as broad, the fourth (c) is the fixed claw 

 and its base, and the fifth the free claw. The articulations of the 

 joints are all oblique. 



