336 PROCEEDINGS OF THE ACADEMY OF 



along most of its length, and ascending with a slightly convex 

 outline forward so as to meet the dorsal margin, which is more 

 nearly horizontal, at a rather acute angle in front ; ej'es, if there 

 are any, unknown. Abdomen or body, with the six segments of 

 nearly equal size, and strongly imbricating. Telson apparentl}^ 

 as long as three of the abdominal segments, flattened, of mode- 

 rate breadth anterior!}', and tapering beliind. Stylets not clearly 

 seen, but apparentlj^ one on each side of the telson; other abdo- 

 minal appendages unknown. Surface of all parts smooth. 



Length of head or cephalothorax, from the anterior to the 

 posterior basal extremities, 0.34 inch; height, 0.18 inch; length of 

 the six body or abdominal segments, 0.51 inch; height, 0.16 inch; 

 leng-th of telson unknown. 



In one of the specimens, there is a leg-like appendage, seen in 

 the matrix extending close along under and parallel to the basal 

 margin of the head or cephalothorax. This appendage, or rather 

 what can be seen of it, consists of three joints, two long and one 

 short. The posterior joint, although apparently broken at the 

 posterior end, is 0.13 inch long, and rather stouter than the next 

 in front of it, which is of the same length. The third joint only 

 shows a little of one end, which connects with the anterior end of 

 the forward one of the two longer joints, and is flexed at right 

 angles to the latter, so as to pass under the anterior margin of the 

 cephalothorax. This may possibly be one of the abdominal ap- 

 pendages, bent forward, but it has more the appearance of a stout 

 antenna bent backward. Prof. Dana thinks it most probably the 

 latter. 



In regard to the affinities of this type, not much can be said 

 without better specimens for comparison. Prof. Dana suggests, 

 however, that it may possibly have some relations to the recent 

 genus Cuma. Being unable to find any defined genus to which 

 it can be properly referred, I propose for its reception a new 

 genus, under the name A7'ch8eocaris, in allusion to the ancient 

 period of its existence. 



Locality and positmi. — Same as preceding. 



[March 19, 



