INVERTEBRATES. 405 



Pal^eocaris typus, M. .and W. 



PI. 32, fig. 5, 5 a, 5 6, 5 c, 5 a". 



Palxocaris typus, Meek and Worthen, March, 1865. Proceedings Acad. Nat. Sci., 

 Philad., p. 49. 



Linear, with thorax slightly wider near the middle than the 

 abdomen ; thoracic and abdominal segments of nearly equal 

 length. Inner antennae equaling the length of the head and 

 thorax ; peduncles stout, first joint a little longer and wider 

 than either of the other two, which are of nearly equal length, 

 and minutely and closely setigerous on their inner margins; 

 flagellum very slender, and minutely jointed ; accessory ap- 

 pendage nearly or quite as long as the flagellum, and scarcely 

 differing from it otherwise. Outer antennae possibly a little 

 longer than the others, peduncles slightly longer than those of 

 the other pair, and like them minutely setigerous in front; basal 

 scales (?) oblong, about as long as first joint of peduncles, 

 squarely truncated. Thoracic legs slender and long, anterior 

 ones apparently not longer or larger than the others, none of 

 them (so far as can be seen) chelate, or with any of the seg- 

 ments enlarged; all the others with the first two or three joints 

 very short; fourth? joint horizontally extended, tapering, and 

 about as long as four segments of the body; succeeding joints 

 (in the specimen examined) very slender and abruptly bent 

 downwards and backwards. Natatory abdominal appendages 

 acutely lancelinear, and some of them as long as four of the 

 abdominal segments. Telson nearly as broad at the base as 

 the penultimate segment, tapering, and as long as two and a 

 half of the abdominal segments ; minutely setigerous on each 

 side. Stylets, with first joint very minute ; second with each 

 division as long as the telson, and lancelinear in form, with 

 pointed extremities, and parallel, more or less setigerous mar- 

 gins. Length of head, thorax and first six abdominal segments, 

 0.78 inch; do. of head, 0.12 inch; do. of the seven thoracic 



