GEOLOGICAL DLSTRTBUTION. 237 



is known from one species in the American Lower Carboniferous. The Lepidocentridae is 

 represented in America by Lepidocentrus whitfieldi sp. nov., also H yattechinus rarispinus (Hall), 

 H. pentagonus sp. nov., and H. beecheri sp. nov., all from the Waverly Group, the basal member 

 of the Lower Carboniferous. The Lepidocentridae also is represented in America by Pholid- 

 echinus brauni gen. et sp. nov., from the Keokuk zone, and in Europe by Koninckocidaris 

 cotteaui Dollo and Buisseret, from Belgium, and Tornquistellus gracilis (Tornquist)" fi'om Ger- 

 many. Of the Palaeechinidae, Maccoya phillipsiae is attributed to the Silurian of England, 

 but with this exception the family of the Palaeechinidae is known only from the Lower Car- 

 boniferous of America and Europe. Of this family the genera Palaeechinus, Maccoya and 

 Lovenechinus are represented by both American and European species, but Oligoporus, is 

 American only. Of the highest genus of the family, Melonechinus, eleven species are American, 

 two are British, and one Russian. Of the Lepidesthidae, most of the species are from the Lower 

 Carboniferous, but two are found in the Devonian as above noted, and two occur in later hori- 

 zons. Lepidechinus, the lowest genus of the family, is known wholly from the Lower Car- 

 boniferous, three species, L. iowensis sp. nov., L. tessellatus sp. nov., and L. imbricatus Hall, 

 being found in America, and one species, L. irregularis (Keeping), in Ireland and France. 

 Perischodomus is represented by one well known species, P. biserialis M'Coy, in the Lower 

 Carboniferous of Ireland and England, and one imperfectly known species in America. Peris- 

 chocidaris is known only from P. harteiana (Baily) in the Lower Carboniferous of Ireland. 

 Proterocidaris is known from the striking species, P. giganteus Koninck, from the Lower Car- 

 boniferous of Belgium. The relatively large genus Lepidesthes has one species in the British 

 Devonian and one in the American Coal Measures, but all others are from the Lower Car- 

 boniferous. Of these, six species are American, one British, and one Russian. As above stated, 

 one species of Pholidocidaris is from the Devonian, but the others known are from the Lower 

 Carboniferous. One species, P. irregularis Meek and Worthen, the best known is American. 

 P. tenuis Tornquist is known in England and Germany and P. gaudryi Julien in France. 



In the Upper Carboniferous, or Coal Measures, the Palaeozoic Echini have dropped out 

 with extreme suddenness and relatively few species are known. The genus Archaeocidaris is 

 represented by 19 species recorded from the Coal Measures, all known fragmentarily only from 

 spines and plates. Seventeen of these have been recorded from America and two from Europe.' 

 Besides Archaeocidaris in the Coal Measures of America is found Lepidesthes extremis sp. nov., 

 structurally and geologically the highest known species of this very interesting genus. 



' The following species of Archaeocidaris have been found in the Coal Measures of North America as recorded by various 

 authors: A. longUpina Newberry, A. agassizi Hall, A. coloradensis nom. nov., A. gracilis Newberry, A. aculeala Shumard 

 and Swallow, A . edgarensis Worthen and Miller, A . trudifer White, A . dininnii White, A . oralis White, A . biangidala Shumard 

 andSwallow, A. ourai/ensis Girty, A. Iriplex White, A. megastyla Shumard and Swallow, A. triserrala Meek, .4. halliana 

 (Geinitz), A. spinoclavala Worthen and Miller, ,4. sp. b. Girty. From Europe there are only two species recorded : .4. 

 paradoxa (Eichwald) in Russia, and specimens which are here referred to A. acanlhifera Trautschold in England. 



