338 PROCEEDINGS OF THE ACADEMY OF [1881. 



•whose width varies in ditferent si)eeies, and according to the 

 position which the arm occupies within the ray (PI. 18, fig. 8). 

 Whenever the respiratory (?) pore is in connection with the arms 

 of the inner part of the ray, it is placed closer to the arm opening 

 than pores whicli are placed toward the outer side. The respiratory 

 (?) pores in the Batocrinites are exceptionally large, sometimes 

 attaining a width equal to one-third that of the arm opening. 

 Their connection with the inner cavity has been explained 

 elsewhere. 



The interradials of the calyx are not numerous, varying from 

 one to four or five, but rarely exceeding three. The first very large, 

 polj'gonal, nearly as large as the primarj^ radials ; it rests between 

 the upper edges of the first radials, between the second, and 

 against the lower sloping edges of the third, and is followed by 

 two or three ver^' much smaller pieces. The anal area has one 

 plate in line with the first radials, of about their size ; there are 

 three plates in the second series, and a few more small pieces 

 above. None of the plates of the interradial or anal series connect 

 with the dome, from which the interradial area of the calyx is 

 separated by the tertiary radials, which meet all around laterally. 

 There are no interaxillary plates, except in the case of B. piano- 

 discus and occasionally in B. trochiscus, in which the arm regions 

 are spread out in width to three times the height of the body. 

 This species has also a greater number of interradials. 



Vault elevated, composed of comparatively- large and heavy 

 pieces, of nearly equal size, even the apical plates, with the excep- 

 tion of the central plate, being but little larger than the rest. The 

 centre piece and the proximal dome plates are much crowded 

 toward the anterior side, owing to the nearlj^ central anal tube, of 

 which, on that side, the large central plate forms the base. The 

 tube is constructed of similar plates as the vault, and very long, 

 sometimes extending more than twice the length of the arms 

 beyond their tips, it is very straight in all cases, and tapers 

 graduall}' almost to a point, with a narrow passage at the upper 

 end. 



Arms fi'om eighteen to twenty-six, or thirt3'-six to fort}', either 

 in pairs or single from each arm opening, round, very short, of 

 medium size and equal width throughout their length. From the 

 body up, they are composed of two series of alternate pieces, and 

 in species which have the double arm structui-e, the first of these 



