G2 Mr. F. A. Bather on Eocidaris and 



Quenstedt himself, as we have already noted, associated 

 Miocidaris coceva and M. keyserlingi. 



From the Cassian and Raiblian beds of Balcony come five 

 or six representatives of this genus, and for two of them new 

 specific names are proposed in my memoir. 



Examination of all this material has led to the following 

 revised and extended Diagnosis of Miocidaris: — 



A Cidarid of moderate size, with the adradial margin of the 

 interambulacrum sharply bevelled on the inner surface, and 

 usually, if not always, denticulate, thus flexibly imbricating 

 over the ambulacrum. Interambulacral plates relatively few, 

 often wide, with scrobicules circular or elliptic, distinct or 

 confluent, with main tubercles small or of medium size, 

 having creiielate bosses. Podial pores not yoked (?). 



The difi'erences between this diagrnosis and the original 

 one of Doederlein are explained and justified in my memoir. 

 AViiat we have now to consider is the inclusion of Eotiaris. 

 Neither in 1899 nor in 1900 did Lambert attempt any diag- 

 nosis for his new genu*, and one must assume that he adopted 

 for it Doederleiu's diagnosis of Eocidaris (1887), since that 

 was based solely on the genotype of Eotiaris, E. keyserlingi. 

 The only difference discoverable between Doederlein's diag- 

 nosis of Eocidaris and his diagnosis of Miocidaris is tiiat the 

 former has " Warzenhofe elliptisch, etwas vertieft, zusim- 

 nienfliessend," while the latter lias " Warzenhofe rund, 

 .scliwach vertieft." Klipstein, however, said of the scrobicule 

 in the holotype of the genotype of Miocidaris (his fig. 15) 

 that it was " sehr stark vertieft." Apart from this flat con- 

 tradiction, the character cannot lead to a true generic division, 

 for the species mentioned above present every degree of varia- 

 tion in this respect. The scrobicules of Miocidaris keyser- 

 lingi are certainly elliptical (or, more correctly, '' meridionally 

 compressed "), but it has been siiown above that they are 

 not always confluent. On tiie other hand, later species of 

 Miocidaris may have compressed and confluent scrobicules. 

 The change from circular to compressed scrobicules is one 

 that takes place during the growth of an individual, and a 

 similar change may take place in racial history, as "does 

 indeed seem to be the case in Triadocidaris. But if so, and 

 in so far as it is of any value, a species witii compressed 

 scrobicules cannot be regarded as the ancestor of one with 

 circular scrobicules ; therefore if Eotiaris has any validity it 

 cannot be the ancestor of Miocidaris, as Lambert maintains. 

 j\ir. Lambert may choose wiiich horn of the dilemma he 

 prefers ; I prefer to drop a genus based on so slight and 

 uncertain a character. 



