FOSSILS OF THE BURLINGTON GROUP. 451 



of each ray, or forty arms to the entire series, all of which 

 are long, slender, and without spines or other asperities. 

 Pinnuhe, or so-called tentacles, slender, rather crowded, 

 and composed of joints that are longer than wide, and 

 deeply furrowed within. 



Surface of body plates marked with small rough ridges, 

 which on the first radial pieces run parallel to the lower and 

 lateral margins, with more or less irregularly disposed gran- 

 ules on the central region, sometimes showing a tendency 

 to radiate from the sinuses for the second radial pieces. 



Hight of body, 0.30 inch; breadth of same, 0.50 inch; 

 length of arms, measuring from the first divisions on the 

 second primary radials. about 1.50 inches ; do., to first bifur- 

 cations above, 0.22 inch ; breadth of each individual arm 

 above all the bifurcations, 0.05 inch. 



This species is related to Plati/crinus Americanins, of Owen and Shu- 

 inard, with which it agrees in the size and form of its body. Its sur- 

 face sculpturing, however, is somewhat different, that species having 

 merely a nodular ridge running along the lower and lateral margins of 

 the first radial plates, and two others starting from the lower lateral 

 angles and converging to the sinuses in the middle of the upper edge, 

 with little isolated nodes on the intermediate spaces ; while in the spe- 

 cies under consideration there are merely three somewhat nodular 

 ridges, parallel to the basal and lateral margins of these plates, with 

 more or less granules in the central region. As such markings, how- 

 ever, are subject to some variation in individuals of the same species of 

 this group, we should not have regarded the differences mentioned of 

 sufficient importance to warrant the establishment of another species, 

 if it were not for the additional fact that Mr. \VACHSMUTH finds speci- 

 mens agreeing exactly with OWEX and SHUMARD'S species in the orna- 

 mentation of the body, and yet having only six arms to each ray, or 

 thirty in the entire series, instead of eight to each ray, as in that under 

 consideration. 



P. TVorf//^/, Hall, agrees with this in having eight arms to the ray, 

 but they are much stouter, and differ in being roughened by numerous 

 small asperities, while its second radial pieces are much smaller, and 

 each supports on each side above only two very short pieces between it 

 and the first bifurcations above, instead of four. Similar differences 

 are also seen in the details of the other divisions, while the surface or- 

 namentation of the two species is entirely different, and the base of the 



