FOSSILS OF THE BURLINGTON GROUP. 



cave, excepting at the lower margin, along which there is 

 also a transverse ridge or caiina. 



Anal plates arranged as in the last described species, in 

 a double alternating series, the lower one being placed 

 obliquely under one side of the first radial on the right, 

 while the next rests upon a short end of one of the sub- 

 radials, the two connecting together and supporting the 

 others above. 



Arms, after their origin on the second radial pieces, each 

 bifurcating on the sixth piece, the two divisions of each 

 being of equal size, but the inner one is simple, while the 

 outer bifurcates again on the sixth, seventh, eighth or ninth 

 piece above the first division, beyond which the two equal 

 divisions are simple as far as they can be traced in the spe- 

 cimens examined. Arm pieces short, or nearly twice as 

 wide as long, wedge-form, and each strongly projecting on 

 the longer side, alternately, so as to present a zigzag ap- 

 pearance ; bifurcating pieces all larger than the others, and 

 extending out, on the dorsal side of the arms, into pointed 

 prominences, sometimes assuming the character of short 

 spines, which, with the lateral processes of the other pieces, 

 give the arms a very rough, harsh appearance. 



Surface of the body plates with deep excavations at the 

 corners, and strong ridges or carina? between the excava- 

 tions. Of these carinse, two descend diverging from the 

 middle of the upper side of the first radials (along which 

 there is also a transverse ridge), to connect with others on 

 the subradial pieces. Sutures between the first and second 

 radial pieces very widely gaping. Column round and very 

 slender near the base, where it is composed of pieces of 

 moderate thickness, every alternate or third one of which 

 projects out distinctly beyond the others. Central canal 

 minute and apparently round. 



Hight of body to the top of the first radial pieces, 0.10 

 inch ; breadth, 0.31 inch ; length of arms, about 1 inch. 



