502 EVECHINUS. 



(HIPPONOE.) Evechinus. 



Evechinus Verrill, 1871, Notes on Radiata. 



This genus is closely allied to Hipponoe, having, when covered with spine?, 

 its general facies; the test is thick, circular, somewhat flattened, and covered 

 with tubercles ot" very unequal size ; the primaries arranged in regular 

 vertical rows; the secondaries irregularly grouped round the base of pri- 

 maries. Poriferous zone broad ; pores arranged in three irregular vertical 

 rows, narrowing towards the actinostomc. Actinostome small ; cuts slight : 

 buccal membrane thin, carrying few plates. Abactinal system prominent ; 

 genital ring narrow; anal system moderate. Spines stout, tapering, rather 

 short, very unequal in size. The close arrangement of the secondaries 

 between the primaries recalls (Psammechinus) Echinus. The poriferous 

 zone of the adult is like that of Hipponoe, while in the young it is like the 

 zone of Echinus, and in other stages the irregular arrangement of the pores 

 recall some of the species of Heliocidaris. as the genus was constituted in 

 the Catalogue Raisonne. 



Evechinus chloroticus 



! Echinus chloroticus Vat.., 184G, Voyage Venus. 



! Evechinus chloroticus Verrill, 1871, Notes on Radiata. 



Pi. IV. f. ; ; PI Vl.f.SO. 



Test moderately thick ; outline from above nearly circular, slightly de- 

 pressed. Actinal region somewhat sunken, in profile regularly arched. Two 

 principal vertical rows of ambulacra! tubercles, with an irregular median 

 row of smaller ones extending from the abactinal to the actinal pole. The 

 ambulacral and interambulacral plates are closely crowded by secondary 

 tubercles arranged in circles round the primaries ; miliaries in plates of both 

 areas few in number. There are six principal vertical rows in the interam- 

 bulacral region ; near the ambitus the exterior rows become somewhat 

 irregular; along the median interambulacral line an irregular or vertical 

 row of smaller tubercles. The poriferous zones are wide, narrowing at the 

 actinal region. The vertical rows of pores are separated by two rows of 

 secondary tubercles, the inner row consisting of the larger tubercles. 



The anal system is small, covered by an outer ring of from nine to eleven 

 plates of uniform size ; the rest of the anal system is filled with small plates 



