MIOCIDARIS. 



characters are of importance if the whole order is to be considered (see pp. -Jill. _>! 1 , but for 

 the Palaeozoic, this is a sufficient diagnosis. It is quite possible thai the D.-vonian 

 Xenocidaris, with three species, considered under Incertae Sedis, Ix-Iongs (,, th<- < 'idaroida. 



Family CIDARIDAE Gray. 

 Cidaridac Gray, 1825, p. 4. 



With characters of the order. 



MIOCIDARIS Doderlein. 



Mioddaris Doderlein, 1887, p. 40; Bather, 1909, p. 61 ; 1909a, pp. 83, 251. 

 Eotiaris Lambert, 1899, p. 82; Lambert and Thiery, 1910, p. 127. 

 Pcrrnocidaris (pars) Lambert, 1899a, p. 39. 

 Eondaris (pars) Lambert and ThieVy, 1910, p. 126. 



Test of moderate size, adradial margin of the interambulacral plates beveled over tho 

 ambulacrals, interambulacral plates relatively few, or many in M. cunmmi, often wide, with 

 scrobicules which are circular or elliptical, distinct or confluent. This genus contains Imt two 

 Palaeozoic representatives, the other species being Triassic or Jurassic. The typepenes as 

 selected by Bather (1909, p. 61) is the Triassic Miocidaris cassinim Hat her <a new name for 

 Cidaris (Mioddaris) klipsteini Desor, which was preoccupied). Dr. Mather (1909: 1909a, 

 pp. 83, 251) has given a critical consideration to this genus and to the speeirs attributed to it. 

 The genus Miocidaris is of especial interest as it contains the geologically oldest known form.- 

 of the Cidaridae, and at the same time the oldest known Echini with two enlumns of plates in 

 each interambulacrum, which is the feature of all modern Echini. Miocidaris ki ;/ rlin</i under 

 various generic names has long been known from the Permian of Europe. I have tin- 

 faction of describing a new species, M. cannoni, from the Lower Carboniferous of America, 

 which greatly extends the geological and geographical range of the genus and family. 



Key to the Palaeozoic Species of Miocidari.t. 



Test small, about six plates in an interambulac-ral column .... M. krt/mrlingi (Grinr 



Test large, about fourteen plates in an interambulacral column .'/. <ininmi sp. nov., p. 5 



*Miocidaris keyserlingi (Geinitz). 

 Text-figs. 238, 238 bis; Plate 9, figs. 1-5. 



Cidaris keyserlingi Geinitz, 1848, p. 16, Plate 7, figs, la, Ib, 2a, 2b. 

 Cidaris verneuiliana King, 1848, pp. 6, 7. 

 Archaeocidaris irrnruiliana King, 1850, p. 53, Plate 6, figs. 2 

 Palaechinus verneuiliana King, 1850, description of Plate 6, figs. 2 

 Eocidaris kaiscrlingii Desor, 1858, p. 156, Plate 21, figs. 15, \(\. 



