116 ECHINOCYPHUS 



Locality and Slratiriraphical Position. — Tliis specimen was collected by Mr. Wiest, from 

 the Chloritic Marl near Charclstock, Somerset, whei'e it is associated with several species 

 of Echinida that are characteristic of the Upper Greensand formation. 



EcHiNocYPHUs, Cotteau, 1860. 



Glyphoctphds (pars), Besor, 1856. 

 Cyphosoma (pars), Woodward, 1857. 

 EcHiNOCTPHUs, Cotteau, 1860. 



Test small, circular, moderately high, more or less inflated on the upper surface, very 

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

 Ambulacra! 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 hoi'izontal impressions. Peristome moderately large, subcircular, sunk in a 

 depression, and provided with slight lobes. Apical disc unknown, opening elongated 

 and subpentagonal, as indicated by the impression. 



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

 genus GlyjjJioci/phus, by others to Cyphosoma. These species, according to M. Cotteau, 

 are distinguished from Glyphocyphis 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. Delamarrei and 

 C. maynificum, 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 Echinocyphus, and impart to the few 

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

 placed them. 



Echinocyphus difficilis, Ayass. PI. XXII, figs. 1 «, i, 3 a, b, c, d, 4. 



Cyphosoma difficile, Ayass. Catal. Syst. Ectyp., Mus. Neocom., p. 12, 1840. 



— — Agassis et Desor. Catal. rais. des Echinid., Ann. Sc. Nat., 



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



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

 DiADEMA ROTULARE, McCoij. Mesozoic Radiatft, Ann. of Nat. History for 



December, 1848. 



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



p. 76, 1854. 



— rotatum, Forl/es. JMeoioirs of Geological Survey, Decade V, p. 3, 



1856. 



