CRUSTACEA. 129 



coarse adpressed tubercles ; abdomen very thick, rounded, nearly 

 twice the length of the carapace, segments nearly smooth, 

 punctured, their extremities broadly falcate ; tail having the 

 crustaceous portion at the outer margin of the base of the two 

 outer pair of fins long, elliptical, strongly serrated on their 

 inner edge. 



In all the characters of generic importance which I have seen 

 in these fossils, they approach the recent Palinuri or spiny lob- 

 sters, with the important exception of the structure of the first 

 pair of feet, which in the recent genus are small, slender, and ter- 

 minated by a simple point for walking only, forming a strong 

 contrast with the present genus, in which they are powerful pre- 

 hensile organs, much more robust than the other feet, broadly 

 dilated towards the end, and terminated by a strong subcheliform 

 claw. I only know the genus in the eocene tertiary strata. 



Archaocarabus Boiverbanki (M'Coy). 



Sp. Char. Carapace about 2 inches 4 lines long and 1 inch 

 9 lines wide, all behind the nuchal sulcus marked with large 

 semioval flattened tubercles, their blunt apices directed for- 

 wards and encircled by a crescent of small pores ; the largest 

 tubercles are about the middle of the back, and have a few 

 small ones irregularly placed in the intervals, towards the side- 

 margins they become smaller and more equal; anterior or 

 cephalic portion more nearly smooth, having only small, sharp, 

 widely separated granules, one on each side of the middle near 

 the base and one or two in the median line near the front 

 xnuch larger than the rest ; front margin with about three den- 

 ticles on each side between the middle and the broad com- 

 pressed horn-like processes at the angles, from each of which 

 latter a ridge extends backwards bearing two or three strong 

 spines ; the anterior prolongation of the cheeks beneath the 

 orbit has also a row of a few large spines : abdomen to end of 

 caudal fins nearly twice as long as the carapace, semicylindrical, 

 nearly smooth, with few distant punctures, the ends of the first 

 five segments abruptly narrowed, thickened and falcately 

 curved backwards, sixth segment having articulated to each end 

 the two thick, elliptical, crustaceous outer marginal supports 

 of the two outer pair of tail-fins ; they are about three times 

 longer than wide, serrated on the inner edge : fo^st pair of feet 

 larger than the others, compressed, penultimate joint dilated 

 towards the extremity into a flattened trigonal hand ; terminal 

 joint forming a strong, subcompressed, curved, moveable finger, 

 as long as the truncated end of the preceding joint, to which 

 it is opposed for prehension, the arm about as long as the leg 



