i 825.] Mr. Grail/ on the Sea Eggs. 423 



Article IV. 



An Attempt to divide the Echinida, or Sea Eggs, into ^Natural 

 Families, By J. E. Gray, Esq. FGS. &c. 



(To the Editors of the Annals of Philosophy/.) 



GENTLEMEN, British Museum, ' 



Lamaeck in his History of Animals without Vertebrae, esta- 

 bhshed as a class of his Apathic animals a very natural group, 

 which he called Radiafa, Mr. Macleay has since proposed to 

 consider this group as equal in rank to the subkingdoms, Verte- 

 brata, Annulosa, Mollusca, &c. 



Lamarck divided his Radiata into two great divisions, which 

 Cuvier placed in distinct parts of his Zoophytes. The former 

 separated the first of his divisions into two, and the second into 

 three sections. Mr. Macleay, in his HoraeEntomologicse (part ii. 

 116), has hinted at the connexion which exists between these 

 five principal constructions, which, if Radiata is to be consi- 

 dered as a subkingdom, should, for uniformity sake, be called 

 classes, although each group formed only a single genus in the 

 works of Linnaeus and his followers. 



The following are the groups proposed by Lamarck and Macleay^ 

 which may be divided in the following manner : — 



1, Normal Group, Echinodermata. 

 Echinida, Mac, Les echinides. Lam, 

 Stellerida, Mac, Les stellerides, Lam, 



2, Annectant Group, 



Medusida, Mac. Les medusaires. Lam, 

 Acalephida, Mac. Les anomales, Lam, 

 Fistuiida, Mac. Les Fistulides, Lam. 



Leaving the determination of the rank which these groups ought 

 to sustain to be considered till more is known of their anatomy 

 and habits, I shall at once proceed to the division of Echinida, 

 the object of my present communication, into families. 



Class 1.? Order 1.? Echinida, Macleay, Les echinides. Lam, 

 Echinus, Lin, Cuv. 



Essential character. — Body not contractile, nor radiately 

 lobed, subglobular, covered with mobile spines ; anus distinct 

 from the mouth. 



These animals are furnished with a distinct crustaceous skele- 

 ton, composed of numerous regularly disposed plates, united by 

 a strait suture, and furnished externally with rounded tubercles, 

 on which mobile spines are attached. These spines are affixed 

 to the base of the tubercles by a circular ligament, and are 



