Miscellaneous. 455 



(1850, ' Prodrome,' i. p, 154) adopted Echinocrinus with Palcrocidaris 

 as a synonym, and left Archceocidar is out of consideration, presumably 

 as a mere MS. name. 



Thus far, then, the result of our examination is to reinstate 

 Echinocrinus Agassiz, with ArchcBOcidaris as a pure homonym and 

 PalcBOcidaris as a synonym. The name ArchgeocidaridaB will also 

 have to go. There remain for consideration various attempts at 

 subdividing the original genus Echinocrinus, or the relegation of 

 certain species to other genera. 



Desor (1857, ' Synopsis,' p. 155) distinguished a new genus 

 Eocidaris from Archcfocidaris (i. e. Echinocrinus) on the ground 

 that the primary tubercles of the interambulacrals were devoid of a 

 halo ("second anneau"), and he included in this genus, inter alia, 

 E. Verneuilana (King), E. rossica (Buch), and E. Munsteriana 

 (Kon.), all species which had at one time been referred to Echino- 

 crinus or Archceocidaris. 



To the interpretation of Eocidaris I shall ask permission to recur 

 in a subsequent note, and confine myself here to pointing out that 

 the result of Desor's action at any rate was to restrict Echinocrinus 

 to species with primary interambulacral tubercles perforate, non- 

 erenelate, scrobiculate, and, above all, annulate (t. e. with a " basal 

 terrace "). 



The next step appears to have been that taken by Meek and 

 Worthen (1869, Proc. Acad. Nat. Sci. Philadelphia), who, after 

 describing Eocidaris '^ squamosa (p. 79), showed its distinction from 

 Archceocidaris and Eocidaris, and tentatively proposed the name 

 Lepidocidaris (p. 81). This resembles Eocidaris in the absence of 

 a basal terrace from the interambulacral primary tubercles, but is 

 presumed to differ from it in the presence of eight columns of inter- 

 ambulacrals at the ambitus and demiplates alternating with primary 

 ambulacrals. The structure of these parts in Eocidaris is still 

 unknown ; but the genus Lepidocidaris has been generally accepted 

 (see Jackson, 1896, p. 220; and Tornquist, 1897, pp. 51 = 773). 



In 1883 Pomel ('Class. Meth.' p. 113) erected the genus Cidaro- 

 tropus, with genotype Archceocidaris Wortheni Hall. Pomel drew 

 no distinction between the interambulacral plates, but based the 

 genus on the two series of regular primai-y ambulacrals, each with 

 two pores in the middle of it. Our knowledge of these structures 

 in the original species of Echinocrinus is not enough to warrant a 

 distinction on these grounds. 



Tornquist, however (1897 *, pp. 52=774), lias divided the sjiocies 

 into two main groups. That including the genotype E. Urii, 

 together with E. Nerei, E. Wervelcei, and E. (Jrueneri, possesses 

 interambulacrals with a clear basal terrace from which thick wedge- 

 shaped ridges radiate to the margin of the plato. The other group, 

 which includes E. rossicus, E. Trautsclioldi, E. Wortheni, E. biancju- 

 latus, E. megasti/lus, and E. Norwoodi, has interambulacrals with a 

 basal terrace well developed on some, but sometimes entirely absent 



* " Das fossilfiihrende Untercarbon &c.,'" Abb. geol. Karte Elsa«s, v. 



