266 THE VOYAGE OF H.M.S. CHALLENGER. 



angle of the basiradial suture, where a radial rests on two basals ; and then the surface 

 of the radials slopes outwards rather more rapidly than that of the basal tube below it, 

 so as to considerably increase the diameter of the cup. All the sutures, interradial, 

 basiradial, and interbasal, are perfectly distinct ; and there is a very faint circular 

 constriction of the basal tube rather below its middle, analogous to that described by 

 Sars in certain individuals of Rhizocrinus lofotensis} This smaller individual has the 

 lowest portions of the arms preserved, the longest of which has small pinnule-stumps on 

 the fourteenth and sixteenth brachials, i.e., on the epizygals of the seventh and eighth 

 syzygial pairs. In the larger individual, however, all the arms are broken away at the 

 syzygy on the distal faces of the first brachials, which are a little higher and more 

 trapezoidal in form than those of the smaller example (PI. LIII. fig. 8). The calyx is 

 also slightly difi'erent in outline. The expansion of the basal tube from below upwards is 

 a trifle more rapid than in the smaller form, so that its outline is less cylindrical ; while 

 the radials are bent outwards a little at about one fourth of their height from their lower 

 angles. This causes the calyx to appear slightly constricted at the highest level of the 

 basiradial suture, a feature which is very marked in some varieties of the adult form. 



As compared with equal sized specimens of Rhizocrimi.^ lofotensis, these young indi- 

 viduals are distinguished by the relatively great height of the calyx, especially in the 

 basal tube, and the expansion at the basiradial suture. The cup of Rhizocrinus lofotensis 

 is not usually so high in projjortion to its width ; and it expands uniformly upwards, 

 from the stem to the upper margin of the radials, so that its shape is pretty regularly 

 obconical {PI. IX. figs. 1,2; PI. X. fig. 2). 



In Rhizocrinus rawsoni, however, the shape of the calyx varies in a most remarkable 

 degree. It is elongated (exceeding 9 mm.) and relatively very narrow in Prof. Perrier's 

 specimens ; while in those lately dredged by Captain Cole ofi" Panama,^ the diameter 

 varies between 80 and 90 per cent, of the length, which is not more than 4 mm. (wood- 

 cut, fig. 19). But as a general rule, the form of the calyx may be described as elongated 

 and subcylindrical. In a few individuals (woodcut, fig. 19, B) it expands uniformly from 

 below upwards throughout its whole length, as is generally the case in Rhizocrinus lofotensis 

 (PI. X. fig. 2). Sometimes the width increases very slowly and sometimes more rapidly, 

 but there is no indication of constriction at any point in the basals or radials. In other 

 specimens the basals expand slowly but uniformly, and the radials slope outwards more 

 strongly, as in PL LIII. fig. 7. Sometimes again, the basals widen a little, but then 

 narrow slightly till they join the radials, which slope outwards so as to again increase 

 the diameter of the cup. 



1 Crinoides vivants, p. 5, Tab i. figs. 35, 39. 



2 I am indebted to Prof. F. J. Bell, F.Z.S., for calling my attention to ttose four remarkable specimens which 

 are divided between the Zoological and Geological Departments at the Museum of Natural History. The keepers of 

 these departments. Dr. A. Giinther, F.R.S., and Dr. H. Woodward, F.R.S., kindly permitted me to examine them, and 

 the former gentleman was good enough to allow the accompanying figures to be made of the two abnormal individuals 

 under his charge. 



