llG 



ECHINOCYPHUS 



Locality and Straiigraphical Position. — This specimen was collected by Mr. Wiest, from 

 the Cliloritic Marl near Charclstock, Somerset, where it is associated with several species 

 of Echinidce that are characteristic of the Upper Greensand formation, 



EcHiNOCYPHUs, Cotteau, 1860. 



Gltphoctphus (pars), Besor, 1856. 

 Cyphosoma (pars), Woodward, 1857. 

 EcHiNOCTPHUs, Cotteau, 1860. 



Test small, circular, moderatel}^ high, more or less inflated on the upper surface, very 

 concave at the base. Poriferous zones straight, and composed of simple pores throughout. 

 Ambulacral and inter-ambulacral tubercles nearly the same size in both areas, bosses 

 crenulated, mammillon not perforated. In many specimens the ambulacra have only one 

 row of tubercles instead of two, their normal number. 



The inter-ambulacral plates are marked at the base with more or less well-marked 

 sutural and horizontal impressions. Peristome moderately large, subcircular, sunk in a 

 depression, and provided with sUght lobes. Apical disc unknoAvn, opening elongated 

 and subpentagonal, as indicated by the impression. 



This genus was established to receive certain species referred by some authors to the 

 genus Glyphocyphus, by others to Cyphosoma. These species, according to M. Cotteau, 

 are distinguished from GlyiAocyphus by their imperforate tubercles, their horizontal sutural 

 impressions, and less solid apical disc. Their crenulated and non -perforated tubercles 

 bring them into near relation with certain species of Cyphosoma, as C. Belamarrei and 

 C. 7nay7iificum, var. sulcatum, which show at the base of their inter-ambulacral plates some 

 traces of sutural impressions ; but these feeble depressions, however, cannot be compared 

 with the deep horizontal grooves that characterize Echinocyphiis, and impart to the few 

 species composing this group the physiognomy of Glyphocypjhus, with which M. Desor 

 placed them. 



EcHiNOOYPHUS DiFFiciLis, Ayass. PI. XXII, figs. 1 «, ^, 2 a, b, c, d, 4. 



Cyphosom.v difficile, Jgass. Catal. Syst. Ectyp., Mus. Neocora., p. 12, 1840. 



— — Agassiz et Desor. Catal. rais. des Echiiiid., Ann. Sc. Nat., 



3e serie, torn, vi, p. 352, 1846. 



— — Bronn. Index Palseontologicus, p. 381, 1848. 

 DiAUEMA ROTULAiiE, McCoy. Mesozoic lladiata, Ann. of Nat. History for 



December, 1848. 



— Maccoyi, Forbes. Catalogue of British Fossils, Morris, 2nd ed., 



p. 76, 1854. 



— KOTATUM, Forbes. Memoirs of Geological Survey, Decade V, p. 3, 



1856. 



