MIOCIDARIS. 245 



characters are of importance if the whole order is to be considered (see pp. 201, 211) but for 

 the Palaeozoic, this is a sufficient diagnosis. It is quite possible that the Devonian genus 

 Xenocidaris, with three species, considered under Incertae Sedis, belongs to the Cidaroida. 



Family CIDARIDAE Gray. 

 Cidaridae Gray, 1825, p. 4. 

 With characters of the order. 



MiociDAKis Doderlein. 



Miocidarls Doderlein, 1887, p. 40; Bather, 1909, p. 61 ; 1909a, pp. S3, 251. 

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

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

 Eocidaris (pars) Lambert and Thiery, 1910, p. 12(). 



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

 ambulacrals, interambulacral plates relatively f€w, or many in M. cannoni, often wide, with 

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

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

 selected by Bather (1909, p. 61) is the Triassic Miocidaris cassiana Bather (a new name for 

 Cidaris (Miocidaris) klipsteini Desor, which was preoccupied). Dr. Bather (1909; 1909a, 

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

 The genus Miocidaris is of especial interest as it contains the geologically oldest known forms 

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

 each interambulacrum, which is the feature of all modern Echini. Miocidaris keyserlingi under 

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

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

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



Kci/ to the Palaeozoic Species of Miocidaris. 



Test small, about six plates in an interambulacral column .... .1/. ke]iserJhi(ji (Geinitz), p. 245. 

 Test large, ai)oiit fourteen plates in an interambulacral column . . . .1/. eannoni sp. nov., p. 247. 



*Miocidaris keyserlingi (Geinitz). 



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



Cidaris kcijserlimji Geinitz, 1848, p. 16, Plate 7, figs, la, lb, 2a, 2b. 

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



Archaeocidaris verneuiliana King, 1850, p. 53, Plate 6, figs. 22-24. 

 Palaechinus verneuiliana King, 1850, description of Plate 6, figs. 22-24. 

 Eocidaris kaiserlingii Desor, 18.58, p. 156, Plate 21, figs. 15, 16. 



