some Species referred to it. 63 



We return now to the statements of Professor Lyman Clark 

 (1907, p. 175), who claims Eocidaris Doederlein as a synonym 

 of Cidaris, and says that Miocidaris is " too near Cidaris 

 and DorocidarisJ^ In two other notes (March and July 

 1908) I have discussed Professor Clark's application of these 

 generic names, and have accepted Doederlein's relegation of 

 Dorocidaris to the synonymy of Cidaris s. str. with genotype 

 C. papillata. Cidaris as restricted by Clark with genotype 

 Cidarites tnetularia Lam. is the genus or subgenus for 

 which Doederlein (Nov. 1906, p. 100) has resuscitated the 

 name Cidarites, but to which he previously (1887, p. 42) 

 applied Pomel's preferable name Eucidaris (1883, p. 109). 

 It is, however, unnecessary for our present purpose to consider 

 all the minor details of tuberculation, of radioles, and of 

 pedicellariae, on which the modern genera, subgenera, or 

 sections are largely based. There are far more important 

 differences in the structure of the test. So far as I have 

 been able to ascertain, the sutures between tiie interambulacral 

 plates in these later genera are plane vertical joints, and do 

 not present the beveh, grooves, and ridges of Miocidaris. 

 At any rate, the sutures between the interambulacra and 

 ambulacra are vertical and notched on the vertical surface 

 for the reception of the ambulacrals ; the firmness of this 

 union is intensified by the thickness and solidity of the united 

 jjlates. In Miocidaris, on the other hand, as first pointed out 

 by Doederlein, the adradial margin of the interambulacrum is 

 bevelled on its inner sixrface so as to slide over the ambu- 

 lacrals, and the grooves, corresponding to the notches in 

 Cidaris, are on the inner face ; the ambulacra also thin off to 

 the etiges, and are throughout much less solid than in later 

 genera. It is only towards the peristome that the plates 

 thicken, to form a perignathic girdle, and that the alradial 

 .'^uture gradually bends to a more vertical position. The 

 perignathic girdle of Miocidaris is even then not so stout as 

 that of Cidaris and Eucidaris, and the auricular processes 

 with which it is provided are nothing like so large or so well 

 developed as in the later genera. Taking the broadest con- 

 struction that anyone nowadays places on Cidaris, it does not 

 seem to me that it can be so extended as to include these 

 Permian and Triassic species. And if this be true of Cidaris 

 in a wide sense, it is still more true of it in the restricted 

 senses of Clark, of Doederlein, or of Mortensen. 



PERMOCIBAItlS. 



There is still one genus needing discussion, namely 

 Fermocidaris Lambert (1900, pp. 39, 47), since tlie genotype 



