400 ARBACIA DUFRESXII. 



of small tubercles. These vertical primary interambulacral rows are placed 

 close to the poriferous zone ; the space between the primary tubercles is 

 completely filled by miliaries, carrying very minute pedicellarise. The granu- 

 lation of the hare median hand is line. The lines of growth of the edge of the 

 plates are well marked, forming colored zigzag lines, parallel to the median 

 interambulacral sutures. Immediately above the ambitus, and over the whole 

 actinal surface of the test, the primary tubercles of the interambulacral spaces 

 are closely packed, arranged in three vertical rows on each side of the median 

 line, forming at same time diagonal rows parallel to the sutures of the plates 

 of the interambulacral system. The tubercles arc largest near ambitus, di- 

 minishing gradually in size towards the actinostome. The median ambulacral 

 space has hut two irregular vertical rows of small tuhercles of uniform size, in- 

 creasing suddenly in size at ambitus, and diminishing towards the actinostome. 

 The lips of the actinal cuts are scarcely marked ; coronal plates narrow and 

 numerous; actinostome proportionally small; abactinal system large, resem- 

 bling in general arrangemeni that of A. punctulata ; the genital plates are 



more rectangular, covered by a closer granulation ; the ocular plates ex- 

 cluded from the anal system, large heart-shaped, extending to limit of the 



genital plates ; genital openings large, close to apex of genital plates : gran- 

 ulation of ocular plates forming indistinct radiating lines from ocular opening. 

 The ten huccal plates of actinal membrane large ; otherwise no specific 

 features in the structure of the huccal membrane. The spines are com- 

 paratively long, and correspond closely to the general appearance of the 

 spines of A. punctulata. In alcohol they are dull violet in color. 



There has always been considerable doubi of the localities of this species. 

 The originals of Blainville were supposed to come from the Banks of New- 

 foundland ; it has heen mentioned as coming from the Sandwich Islands, and 

 the West Coast of Africa was also supposed to he its true locality. Dr. Cun- 

 ningham has collected quite a number of specimens, now deposited in the 

 British Museum, in the Straits of Magellan: there are also specimens from 

 Chili in the Ecole des Mines. So that, whatever may he the ultimate range 

 of this species, it is, like the other species of the genus, essentially American. 



Philippi has described this species from Chili, under the name of E. 

 Schythei. 



