ORDER II 



EUECHINOIDEA DIADEMATOIDA 



229 



small, smooth, primary tubercles. lAmb tubercles replaced abactinally by 

 warty or irregular elongate elevations. Epistroma much developed. Abun- 

 dant in Upper Jura. 



Family 3. Diadematidae. Wright. 



Test Uighbj ormnwnfeil, hnnlil, depressed, or spheroidal Ambulacra straight, 

 moderately broad or narrow, with vertical 

 rows of small primary tubercles, and com- 

 pound plates near the ambitus and actin- 

 ally. Interambulacra broad, with numer- 

 ous low plates; the rows of primary 

 fill" rdes diminishing in number dorsally. 

 Peristome large, polygonal. Lias to 

 Recent. 



Sub-Family A. DIADEM ATINAE. 



Ambulacral plates compound near the 

 tinnitus; pairs of pores in simple vertical 

 3 or in arcs of three. 



Desor), (Fig. 368). Amb narrow, often 

 projecting ; two vertical rows of small, 

 primary, crenulate, and perforate 

 tubercles extending from peristome 

 to apex. I Amb with two or more 



" . Dlndfiina (Pseudodiadcma) negleclum, Tlumn. From 



vertical rOWS OI primary tubercles the Bernese Jura. A, Ii, Profile and ventral aspect of 

 resembling those Of the Amb, but tCSt ' 1/1 ' <?, Ambulacrum, enlarged. A Spine, Vi. 



larger. Secondary tubercles and granules surrounding the scrobicules. 

 Spines long, hollow, longitudinally striated. Lias to Recent. 



Duncan has shown that the separation of the fossil species from the recent under Desor's 

 term of Psciidodiadema is a purely artificial distinction. The following sub-genera are 



? 3 fl J A T .^ T)-J-~ . . T> If! ?_ -7 /"1-A.L T' T\ 7 



recognised: Centrostejjfianus, Peters ; Recent. 

 A a 



Microdiadema, Cotteau ; Lias. Diademopsis, 



Fio. 369. 



Codiopsis doma, Desm. sp. Cenomanian (Tourtia) ; Tournay, Belgium. A. Side-view of test, Vi- A Ventral 

 aspect of same. C, Apical system, enlarged. 



Desor ; Lias. Echinodiadcma, Cotteau ; Upper Jura. Hemipedina, Wright ; Jura, Cretaceous, 

 and Recent. The latter differs from Diadema in having simple Amb plates near the apex, 

 and perforate, but not crenulate tubercles. 



Heterodiadema, Cott. Like Diadema, but with the apical system greatly 



