&EKEEA AND GEOTJPS OF THE ECHINOIBEA. 245 



the genus from Metalia, a division of the genus Brisms 

 (p. 51). His types were Plagionotus pectoralis and P. Desorii. 

 Brissus sternalis, Lamk., sp., was his type of Metalia. A. Agassiz, 

 1872, Eevisiou, p. 144, placed Plagionotus and Metalia as syno- 

 nymous, and cliose the latter subgeneric name to include Pla- 

 gionotus pectoralis and Metalia sternalis. Since the time of the 

 ' "Revision,' the describers of recent Echinoidea have followed 

 A. Agassiz ; but that excellent palseoutologist Dames has placed 

 Brissopsis and Toxohnssus as synonyms of Metalia. It appears 

 correct to admit the name Metalia instead of Plagionotus, to unite 

 the species separated by Grray under this genus, and to place 

 Brissopsis as an independent genus, with Toxohrissus and Kleinia 

 as its synonyms, 



Grenus Metalia, Grray, 1855 (division), Gat. Bee. Ech. Brit. 



Mus. pt. i. p. 51. A. Agassiz, 1872 (subgenus), Bevision, 



pp. 144, 360. Loven, 1874, Etudes, pi. 40, sub Plagionotus. 



{Enlarged.) 



Syn. Plagionotus, Ag. and Desor, 1847, Grray, 1855, Liitken, 



1863; Xantholrissus, A. Ag., 1863; Brissus, Martens, 1869; 



Brissopsis, sensu Dames, 1877. 



Test thin, moderate to very large, depressed, elliptical or ovoid 

 in more or less wavy marginal outline, slightly indented ante- 

 riorly and truncated posteriorly, lowly arched or nearly flat ab- 

 actinally, tumid above the margin, the edge of which is sharp ; 

 actinally comparatively flat. 



Apical system excentric in front ; the four basal plates per- 

 forated; the madreporite extending centrally and posteriorly, 

 separating the postero-lateral basal and radial plates- 

 Ambulacra diverse ; the anterior in a very shallow groove 

 which may be absent near the apex, its pairs of pores rather 

 distant and small ; the petaloid parts of the paired ambulacra in 

 variably sunken grooves, narrow, unequal and long, their pairs 

 of pores large, nearly closing, with narrow interporiferous areas ; 

 anterior petals divergent, long, and straight or curved, those of 

 the postero-lateral petals similar but rather close, and the zones 

 bending with the distal ends flaring outwards or not, longer than 

 those of the antero-lateral : actinally the postero-lateral ambu- 

 lacral areas are long and narrow. 



Interradia large, especially actinally, where the second and 



