INVERTEBRATES. 403 



ACANTHOTELSON IN^EQUALIS, M. and "W. 



PI. 32, fig. 7, la. 



Acanthotelson inxqualis, Meek and Worthen, March, 1865, Proceed. Acad. Nat. Sci., 

 Philad., p. 48. 



The specimen* upon which we proposed to found this species appears to agree 

 with the last in almost every respect, excepting in the proportional size and 

 the form of the segments. In the first place, the penultimate abdominal seg- 

 ment is nearly twice the length of any of the others, instead of being nearly or 

 quite of the same length; while the other abdominal segments (as seen in a side 

 view) are more cuneiform than in the last. Again, the fifth and sixth thoracic 

 segments are longer, particularly above, and the fourth shorter, than any of the 

 others, instead of all being of about the same length. We have not been able 

 to see the stylets, nor to make out the nature of the legs; but from a part of one 

 of those of the anterior pair, they would seem to be rather stouter than in the 

 last described species. 



As these differences can scarcely be due to accidental distortion, we can but 

 regard this form, with the material now at hand for comparison, as a distinct 

 species. If we are correct in this view, it is probable good examples will show 

 other differences than those mentioned above. 



Length of head, thorax and abdomen, 0.90 inch; length of head, 0.12 inch; 

 length of the seven thoracic segments, about 0.50 ineh; length of first five abdo- 

 minal segments, 0.26 inch; length of penultimate abdominal segment, 0.09 inch. 

 Height of third abdominal segment (flattened side view), 0.13 inch; height of 

 anterior thoracic segments, about 0.07 inch. Length of lower antennae at least 

 0.43 inch; length of upper not less than 0.36 inch, and probably a little more. 



Locality and position : Same as last. 



Genus PAL^EOCARIS, M. and W. 



(italaior, ancient; xapic,, a shrimp.) 

 Palxocaris, Meek and Worthen, March, 1865. Proceed. Acad. Nat. Sci., Philad., p. 48. 



Inner and outer pairs of antennas of nearly equal length, 

 the former each bearing a well developed accessory appendage; 

 peduncles of both pairs shorter than the flagella. Head about 

 as long as the first two abdominal segments. Thoracic legs 



