CALAMOCRINUS DIOMED^. 21 



has syzygies at the lirst, third, and lifth joints. There are only eleven 

 joints of this arm preserved, and live of the stem beyond this. 



In the left arm of Plate IV. Fig. 1, the eighth joint is the axillary of the 

 first fork to the right. The first, fourth, and sixth joints have syzygies. 

 The first pinnule is on the third joint. The second pinnule is on the epi- 

 zygial of the fourth joint. The third pinnule is on the epizygial of the 

 fifth joint. The fourth pinnule is on the epizygial of the sixth joint. 

 Of the first branch on the right only forty-two joints are preserved. It 

 has syzygies on the second, third, and thirteenth joints. At the seventh 

 joint the main stem branches again on the left; the third joint has a 

 syzygy. Only two joints of the left branch are preserved. The main 

 stem branches again to the right on the seventh joint ; the second joint 

 has a syzygy. Only three joints of this branch are preserved. 



The main stem branches again to the left on the ninth joint. The third 

 and seventh joints have syzygies. Only three joints of the main stem and 

 only three of the branch remain. 



The arm on the right in Plate IV. Fig. 1, has syzygies on the first and 

 second joints. The first pinnule is on the third joint. The fifth joint has 

 a syzygy, and also the sixth. The arm branches on the eighth joint. The 

 second pinnule is on the right, and is on the epiz3-gial of the fourth joint; 

 the third pinnule is on the epizygial of the fifth joint, and the fourth on 

 that of the sixth. 



Seen in profile, the arm joints of the branches are deeply indented for 

 the insertion of the base of the pinnule ; the lower joint, the pinnule of 

 which is on the other side, having a longer face than the upper one, pro- 

 jects, when seen in profile, into a triangular point with rounded ends formed 

 from its junction with the trapezoidal outline of the lower face (Plate I. 

 Figs. 1, 7). 



Seen from above, tlie lines of joints of the lower brachials are more or 

 less parallel (Plate III. Figs. 1, 2), while the alternating long and short sides 

 of succeeding brachials become more and more prominent, as well as more 

 and more regular, as we pass from the first axillary along the main stem, 

 and to each of the branches towards the extremity of the arm. 



The position of the first pinnule in genera allied to Calamocrinus seems 

 to be very variable. In Hyocrinus it is the third brachial ; in Bathycrinus 

 the third brachial is the first axillary ; in Rhizocrinus the first pinnule is 

 on the third or fourth brachial ; that is, if we regard as a single joint 



