Echinoid Tests, Biademoida. 
101 
147), places it in a Tribe Eodiademinae of the Subfamily Tiarinae of the Family 
Diadematidae. Gregory (1900), who raises the Orthopsinae to the rank of a Family — 
Orthopsidae, retains Eodiadenia therein. Delage & Herouard (1904), refer Eodiadema 
to their Aspidodiademinae (= Aspidodiadematidae Duncan), while placing Orthopsis 
and most of its allies in Pedinidae. Gregory (loc. eit.) included Aspidodiadema in 
the Orthopsidae, a reference which may or may not be justified; but the action of 
Delage & Herouard seems illogical. For, whatever Eodiadema may be, it is undoubt- 
edly, both by time and structure, an ancestral form of the Diadematoid urchins. 
To comprise such a form together with a couple of recent genera in one Family, 
while removing all allies and intermediate genera to other Families, could be just¬ 
ified only by the wildly improbable assumption that there existed a long intervening 
series of Jurassic, Cretaceous, and Tertiary genera of Aspidodiadematidae still com- 
pletely unknown. 
The following are the chief specimens of «Echinus minutus » in the British 
Museum. — E8808—E8812, cotypes of J. Buckman’s description in Murchison's 
«Geology of Cheltenham» p. 95, Edit. II, 1844; Edit. III, 1845, from the Lower 
Lias, Oxynotus shales, between Cheltenham and Gloucester. E8813, a sixth cotype, 
appears to be from the second type-locality, the Upper Lias of Alderton Hill, and 
is probably a different species. E8814, original of T. Wright, Palaeont. Soc. Monogr. 
Ool. Echin., p. 230. pl. xvii, f. 2. E8815, original of T. Wright, op. cit. pl. xv, 
f. 3a. E8816, figured and described as Acrosalenia crinifera (Quenst.) by T. Wright, 
Ann. Mag. Nat. Hist. (2) xiii, p. 168, pl. xii, f. 1. All these three are from the 
Oxynotus shales near Lansdown in Cheltenham. To save future confusion I hereby 
make E8808 the lectotype of the species. Examination of these specimens inclines 
me to regard Echinus minutus as not congeneric with Eodiadenia granulatum. 
But admitting some relationship, I would suggest that these two species at any rate 
might come at the base of the Acrosaleniidae. Duncan said of Eodiadema , 
«The similarity of the genus to Acrosalenia is striking» ; and Wright placed Echinus 
minutus in Acrosalenia. Both species differ from Acrosalenia in the simplicity 
of the ambulacrals, and, in the supposed absence of suranal plates. E. granulatum, 
however, shows a posterior shifdng of the periproct while in E. minutus the space 
left by the caducous apical System usually displays an asymmetry that may be due 
to the same cause. 
Lambert (1900, p. 35) has referred to the genus, as emended by him, the 
following species, in addition to the genotype, which is of Upper Pliensbachian age: 
Cidaris regularis Münst., including C. Admeto Münst. non Quenst. 
Pseudodiadema lohatum Wright. 
Pseudodiadema Collenoti Cotteau .. 
Echinus minutus J. Buckman. 
Acrosalenia parva Wright. 
Cidaris laqueatus Quenstedt . 
Cidaris octoceps Quenstedt. 
Eodiadema pusillum Lambert. 
Carnian 
Hettangian 
» 
Sinemurian 1 
» 1 
Pliensbachian 
Toarcian 
» 
In making C. Admeto a synonym of C. regularis, Lambert follows the 
1 Lambert’s reference of these two species to the Charmouthian (= Pliensbachian) was probably a slip. 
