GENEEA AND GKOTJPS OF THE ECHIKOIDEA. 129 



Greuiis Leiopedina, Gotteau, 1866, Bev. et Mag. de Zool. ser. 2, 

 vol. xviii. p. 206. {Amended.) 



Syu. Chrysomelon., Laube, 1869, Ecli. Vincent. Tert., Denks. d. 

 k. Akad. Wiss. Wien, 2 Abth. p. 13. 



Test large, swollen, prolate spheroidal or globular, subcorneal 

 dorsally, broadest beneath the equator, and subpentagoual or 

 circular in marginal outline. 



Apical system central, small, flush. 



Ambulacra long, straight, very broad ; poriferous zones broad, 

 with vertically close, triserial pairs of pores almost horizontal ; 

 usually the pair nearest the interporiferous area the largest, the 

 pores of it being elongate, those of the other pairs circular. 

 Plates very numerous, low, broad, compound, composed of a large 

 adoral primary plate, a median demi-plate, and a very low aboral 

 primary plate. The adoral and aboral pairs of pores of a triplet 

 remote from the interradium ; the median pair in the demi-plate, 

 close to it. Tubercles of the interporiferous areas small, distant, 

 finely perforate, plain, subscrobiculate, in two, distant, vertical 

 rows. Grranules between the tubercles homogeneous. 



Interradia broad, with two vertical rows of tubercles similar to 

 those of the ambulacra, with intermediate granules, some of which 

 may have mamelons near the apical system. 



Peristome small, subclrcular, flush ; amount of branchial incision 

 variable. 



Fossil. Eocene : Europe. 



G-enus Htpechinus, Desor, 1858, Synopsis, p. 130, pi. xviii. 



Test moderate in size, tumid at the circular ambitus, nearly 

 hemispherical dorsally, but slightly depressed. 



Ambulacra with wide poriferous zones ; pairs of pores in oblique 

 triple series ; plates low, comj)ouud ; the median pair of pores 

 being in a demi-plate, and placed nearer the interradial suture 

 than the other pairs ; the adoral pair very remote from the 

 interradial suture and in a primary plate. Interporiferous 

 areas with two vertical rows of small, numerous, plain primary 

 tubercles, which are much larger actiually than above the 

 ambitus. 



Interradia with numerous coronal plates ; the primary tubercles 

 imperforate and plain, in two distant vertical rows ; the tubercles 



LINU. JOUaW. — ZOOLOGY, VOL. XXIII. 9 



