CRINOIDS AND BLASTOIDS. 173 



ondary radials 2x2x5, the upper ones axillary; succeeded by two 

 cuueate fixed brachials, each supporting an arm, giving normally 

 four arms to the ray, or twenty in all. Arms biserial, moderately 

 strong, rounded, the tips slightly incurved and somewhat flattened. 



Interradials rarely more than three, sometimes but two. The 

 first one very large, extending to the full length of first secondary 

 radials: those of the second range small. None of these plates 

 connect with the interradials of the vault, except those of the 

 azygous side, and therefore the plates forming the bases of the 

 arms are united laterally. The first anal plate has the form of 

 the first radials, and supports upon its truncate upper side 

 another anal piece, which rests between two large interradials. 

 All three plates are nearly of equal size, and as high, if not quite 

 as wide, as the corresponding single plate of the four regular 

 sides. There are two or three small plates above, and a single 

 piece between the arm bases. The interradials of the ventral side 

 are numerous, small, slightly convex. Ventral tube subcentral, 

 long, slender, extending beyond the tips of the arms. Ventral 

 side broadly convex, somewhat lobed; composed of numerous 

 small convex plates, among which the summit plates are well de- 

 fined, the central one forming the base of the tube. 



Column short, the nodal joints in the upper part large, rounded 

 on the edges; the intermediate joints comparatively small and 

 short, contrasting strongly with the others. At the lower 

 end the joints are more uniform. The column has been ob- 

 served by us to its full length in several specimens, and in all of 

 them it is short, not to exceed six inches. It tapers all the way 

 gradually to its distal end, where it terminates in a sharp point. 

 The lower part, to about one-third of its whole length, bears 

 short lateral cirrhi, which are arranged singly, not in whorls, there 

 being but one to a joint. 



Geological position, etc. The same as the preceding species. 



Our own collection. 



GENUS DORYCRINUS Roemer. 



The three species of Dorycrinus herein described are very in- 

 teresting as illustrating the close affinities which exist between 

 B&tocrinns, Eretmocrinus and Dorycrinus, for which we pro- 



