﻿CALLIDERMA. 5 



tubercle-like granule. Actinal interradial areas large, confined to the disk. 

 Actinal intermediate plates large, covered with granules [and in the recent species 

 bearing one or occasionally two compressed acute papilliform spinelets]. Arma- 

 ture of the adambulacral plates arranged in longitudinal series. 



This genus was established by Dr. J. B. Gray for the reception of a recent 

 Starfish, the type of which is preserved in the British Museum. It was described 

 under the name of Calliderma Emma. In his remarks which follow the diagnosis, 

 Dr. Gray observes 1 that "there is a fossil species, very like the one here 

 described, found in the chalk, and figured in Mr. Dixon's work on the fossils of 

 "Worthing, which I propose to call Calliderma Dixonii." I have not been able to 

 trace which of the fossil species is here referred to, but that is a circumstance of 

 no great importance, as the forms figured in Mr. Dixon's work on ' The Geology 

 of Sussex ' were described and named by the late Prof. Edward Forbes. It is inter- 

 esting, however, to note that the resemblance of some of the Cretaceous forms to 

 the genus Calliderma had actually been observed by the author of that genus. 



Thanks to the careful study and critical insight of Mr. J. Walter Gregory, of 

 the British Museum, a number of the examples which now form part of the 

 National Collection have been correctly, as I think, referred to the genus Calli- 

 derma, and already bear that name upon the manuscript labels attached by him to 

 the specimens. 



There are, however, some differences between the fossil forms and the recent 

 type. The most notable perhaps being the character presented by the spinulation 

 of the marginal, the abactinal, and the actinal intermediate plates in the recent 

 species, as compared with the fossil examples, whose state of preservation does not 

 permit of our positively asserting whether the same character was present in their 

 case or not. I am inclined to think that this uncertainty does not necessarily 

 invalidate the reference of the fossil forms to the genus, and I consider it highly 

 probable that species might exist which did not bear incipient spinelets on the 

 plates in which they are found in the solitary existing species with which we are 

 acquainted. The peculiar pits found upon the plates in some of the fossil examples 

 may indicate the former presence of these spinelets, although, for my own part, I 

 am more disposed to believe that in the majority of cases the depressions in 

 question are structures associated with a pedicellarian apparatus. (See, for ex- 

 ample, PL I, figs. 1 a, 1 b, 1 c, 1 d; PI. Ill, fig. 3a; PI. V, figs. 2 a, 2 b, 2 d.) 

 In other cases it is certain that little spinelets did exist, as in the tip of the ray 

 shown in PI. VIII, fig. 2 a ; also, but perhaps more doubtfully, in PL VII, figs. 

 4 a, 4 c. 



1 ' Proc. Zool. Soc. Lond.,' part xv, 1847, p. 76; ' Synop. Spec. Starf. Brit. Mus.,' London, 

 18G6, p. 7. 



