324 FOREIGN JURASSIC COLLYRITID^. 



square behind ; upper surface convex, base flat ; ambulacra narrow ; anterior summit 

 removed to a considerable distance from the posterior summit ; apical disc small, square, 

 vent pyriform, supra-marginal ; peristome extremely excentral. 



Dimensions. — Height, six tenths of an inch ; breadth, seven tenths ; length, one 

 inch. 



Formations. — Great Oolite, Saint-Marceau, (Sarthe), Etage, Callovien, Hornussen, 

 Kornberg (Argovia), Erlinsbach, and Pouillerel, near Chaux-de-Fonds, 

 Switzerland. 



Collections. — MM. Gueranger, Moesch, Cartier, Nicolet, Mus. Neuchatel. Rare. 



CoLLYRiTES ELLIPTIC A, Lamk. Syu. Disaster ellipticus, Desor. Monographic des 



Disaster, tab. ii, figs. 5 — 7. 



Test regularly elliptical, convex above, more or less depressed, plano-convex below ; 

 the apices of the posterior ambulacra converge at a point about one third of the distance 

 between the vent and the anterior summit, which is more or less excentrally forwards. 



Dimensions. — This species varies very much in size and relative dimensions, the 

 following is M. Cotteau's estimate from abundant materials : — " a. 

 Circular variety. — Height twenty millimetres ; transverse diameter, 

 forty millimetres ; antero-posterior diameter equal to the transverse. 

 B. Elongated variety. — Height twenty-three millimetres; transverse 

 diameter, thirty-eight millimetres ; antero-posterior diameter, forty-two 

 millimetres, c. Large variety. — Height forty millimetres ; transverse 

 diameter, sixty millimetres ; antero-posterior diameter, sixty-three 

 millimetres. (This is the Disaster malum, Ag.)" 



Formation. — Kellovian, Chaufour, Mamers, " Kelloway Ferrugineux." (Sarthe.) 



Collections. — Very common in most collections. I have a fine series in my cabinet, 

 sent by M. Triger, M. Cotteau, and M. Michelin, from this locality. 



CoLLYiiiTES PiNGUis, Dcsor. Syuopsis des Echinides Fossiles, p. 205. 



Test dci)ressed, of an elliptical form, with the border inflated, resembling C. hicordata a 

 little, but larger than that form ; posterior ambulacra nearly straight and rising much 

 higher than the vent. 



Formation. — Oxfordian superior of Botzberg, and Geisberg, near Brugg (Argovia). 



Collections. — Mus. Bale, Coll. MM. Grossly, Schmiedlin, and Cotteau. 



