38 



1. ECHINOLAMPAS DEPRESSUS. 



Ovate, depressed, subpentangular ; back regularly convex. 



Hab. ? 



Genus Mortonia. 



Shell ovate, thin, rather produced in front, rounded behind, co- 

 vered with small tubercles ; vertex central, convex ; internal cavity 

 quite simple ; ambulacra petaloid, narrow, open at the end ; bands 

 rather diverging ; pores rather crowded, united by an oblong groove ; 

 beneath concave, especially near the mouth and vent ; mouth rather 

 large, roundish oblong, transverse, without any ambulacral star ; vent 

 large, transverse, oblong, in the middle of the space between tha 

 mouth and hinder edge ; ovarial pores four ; madreporiform plate 

 small, central. 



1 Echinocyamus, sp., Desmoulin. 



Mortonia, Gray, Cat. Echinoida in Brit. Mus. 



This genus differs from Echinocyaniis in the thinness of the shell, 

 and especially in the ambulacra being larger, more perfect, and in the 

 pores of the ambulacra being united in pairs by a cross groove. It 

 differs from the fossil genus Pygaidus in the vent being inferior, in- 

 termediate between the mouth and edge, and transverse. 



This genus is named after Dr. Morton, the historian of Northamp- 

 tonshire, who first attempted to arrange the fossil Echini into generic 

 groups. 



Mortonia australis. 



Elliptical, depressed, rather acute in front, rounded behind, under 

 side concave near the mouth and vent ; vent large, oblong, trans- 

 verse, in the centre between the mouth and hinder margin. 



Fibularia australis, Desm. Tab. Syn. 240. 



Echinocyamus australis, Agassiz et Desor, I. c. 140. 



Hab. South Sea. Mallet. 



February 11, 1851. 



William Yarrell, Esq., Vice-President, in the Chair. 



The following papers were read : — 



1. Description of a new genus and family of Cyclosau- 

 RiAN Lizards, from Para. By J. E. Gray, Esq., F.B.S., 

 P.B.S. 



(Reptilia, PI. VI.) 



This interesting Lizard has lately been purchased by the Museum, 

 from a collection of Saurians recently made by Messrs. Wallace and 

 Bates, during their excursion within a circuit of about 300 miles of 

 Para. 



