CALAMOCRINUS DIOMED^ 50 



the axial cord opening These ridges are similar to those of the fai 

 the top stem joint, but less prominent, and similar to those of the corre- 

 sponding parts in the Apiocrinida, figured by D'Orbigny and de Loriol, 



We do not find in the top stem joint of Calamocrinua the distinct ele- 

 vations ami depressions for the reception of the basals characteristic of 

 the Apiocrinidaa. 



It is interesting to note so marked a difference in the structure of the 

 faces of the stem joints in Calamocrinus, Apiocrinus, Millericrinus, and the 

 like, when contrasted with the bifascial faces of the lower part of the stem 

 joints of Rhizocrinus and Bathycrinus. No such bifascial faces are found in 

 the former genera, while the faces of the upper stem joints of Rhizocrinus, 

 of Hyocrinus, and of Bathycrinus show no such structure as characterizes 

 the lower stem joints. 



It is interesting also to observe here, what does not seem to have been 

 noticed by previous writers who have examined Rhizocrinus, that the up 

 per stem joint is convex at its upper face, and that in the concave space of 

 the basal ring is found a delicate, exceedingly thin five-lobed young joint, 

 entirely hidden within the basal ring. This young joint is apparently 

 identical with the similar joint described in Calamocrinus. The top si em 

 joint was three times as wide as high, and followed in the specimen exam- 

 ined by two similar joints ; the fourth joint was nearly as high as wide, 

 while the fifth joint was higher than wide. Neither of these five joints 

 possessed bifascial faces. They were slightly convex on the outer edges 

 of the upper face, with a depression towards the axial canal. 



The stem joints of Hyocrinus, which hear the closest resemblance to those 

 of the Apiocrinidae, have been described by Sir Wyville Thomson,* and 

 also by Carpenter.! They vary considerably, some being ".perfectly plain," 

 others " being marked with a pattern of radiating grooves and ridges." 



We know nothing as yet of the root of Hyocrinus, hut in the case of 

 Rhizocrinus, at least, the structure of the root, branching into numerous 

 rootlets, plainly indicated that it was adapted to thrive in a muddy or soft 

 bottom ; and such was generally the character of the ground upon which 

 the " Blake " dredgings showed it to be most abundant. In the case of 

 the Apiocrinidaa proper, however, they (Guettardicrinus, Millericrinus, | Apio- 



* Journ. Linn Soc. 1S78. Vol. X.II. p. 5:5. t Chall. Rep., p 32, Plate V c. Figs. A. 5. 



t P. H. Carpenter considers Millericrinus Pratti and other Apiocrinidae as not having lived at- 

 tached, but with a free extremity, as in Wbodocrinus. See his paper on Millericrinus Pratti. Q. .1. 

 Geol. Soc. London. 18S2. 



