CLARK: THE CIDAIUDAE. 175 



To these I have given special attention, but the great majority do not 

 seem to me to be based on sufficiently reliable or tangible characters to 

 warrant their recognition. The following list includes them all, with 

 my opinion as to the proper status of each ; those which appear to me 

 to be worthy of use are indicated by black-faced type. 



Rhabdocidaris Desor : not distinguishable from Phyllacanthus. 



Leiocidaris Dcsor : " " " 



Eocidaris Ucsor : not distinguishable from Cidaris, or else from Archaeocidaris, 

 according to what species is considered the type. It is true that the first 

 species mentioned by Desor (keyserlingi) does not agree with the diagnosis 

 of the genus, but since Doderlein ('87) has definitely selected that species as 

 the genotype, Eocidaris becomes a synonym of Cidaris. 



Leptocidaris Quenstedt : very probably not one of the Cidaridae. 



Gymnocidaris A. Ag. : not distinguishable from Cidaris. 



Prionocidaris A. Ag. : " " " Phyllacanthus. 



SchleinitziaStuder: 



Tylocidaris Pomel : apparently a valid genus, though allied to Cidaris. 



Typocidaris Pomel : not clearly distinguishable, and too near Cidaris and Doro- 

 cidaris. 



Pleurocidaris Pomel : not distinguishable from Phyllacanthus. 



Plegiocidaris "j 



Paracidans p omel ; hopelessl y indistinguishable. 



Procidaris 



Eucidaris ' 



Auaulocidaris Zittel : not distinguishable from Cidaris. 



Discocidaris Doderlein : not " " Goniocidaris. 



Mikrocidans ] D5( j er lein : not distinguishable from each other and too near 



Tnadocidaris cidaris and Dorocidaris . 



Miocidans J 



Phalacrocidaris l Lambert : ? 



Aulacocidaris 1 Lambert : ? 



Tretocidaris Mortensen : see below. 



Schizocidaris Mortensen : not worthy of separation from Goniocidaris. 



Petalocidaris Mortensen: " 



Histocidaris Mortensen : " " " " " Porocidaris. 



1 I liave been unable to see the original descriptions or any figures of these two 

 genera, as the papers in which they are published are not to be found in either 

 Cambridge or Boston. But Aulacocidaris (Lambert, 1903; Bull. Soc. Hist. Nat. 

 Savoie, (2) VIII, p. 222) is evidently closely related to Phyllacanthus and is proba- 

 bly not distinguishable, while Phalacrocidaris (Lambert, 1902; Mem. Soc. Geol. 

 France, Pal. IX, fasc. Ill, Mem. 24, p. 27) is based on Doderlein's living species of 

 Stereocidaris from Japan, but includes a number of fossil forms. As Stereocidaris 

 is itself only distinguishable with great difficulty, it is very unlikely that Phalacro- 

 cidaris is tenable. 



