174 Prof. F. M‘Coy on the Classification of 
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. 
Archeocarabus Bowerbanki (M‘Coy). 
Sp. Char. Carapace about 2 mches 4 lines long and 1 inch 
9 lines wide, all behind the nuchal suleus 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 
much 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 bearimg 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: first 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 
