AGASSIZIA EXCENTRICA. 353 



BRISSINA. 



Subfamily Brissina Gray, 1855. Cat. Rec. Ech. 



AGASSIZIA. 



Agassi zia Val. 1846. Voyage Venus, Atlas. 



Test thin, ovoid, differing from all other Spatangoids in having the anterior 

 pair of petals composed of single poriferous zones. Peripetalons fasciole and 

 lateral fasciole connected and passing under anus. 



Agassizia excentrica 



! Agassizia excentrica A. Agass. 1869. Bull. M. C. Z., No. 9, I. p. 276. 



PI. XIV f. 9 - 12 ; PI. XP. f. 23, 24. 



I am somewliat inclined to consider this species as the Agassizia porifera ; 

 but not having any original specimens for comparison, and the drawings of 

 Ravenel and McCrady showing rather striking differences, I will not take 

 their identity for granted, and compare it only with its West Coast repre- 

 sentative, from which it can at once be recognized by the position of the 

 apical system, which is much more eccentric posteriorly ; on this account 

 the disparity between the odd anterior pair of ambulacra and the posterior 

 pair is greater than in that species. The interambulacral plastron is ellip- 

 tical, and with this exception the arrangement and proportion of the tuber- 

 cles is that of A. scrobiculata Val. The peripetalons fasciole does not pass 

 below the ambitus, and the posterior fasciole makes a sharp angle under the 

 anal opening. Only two denuded tests were collected, so that no further 

 details can be given about this species. 



From 36 to 115 fathoms. 



It is with considerable doubt that I refer to Agassizia small Spatangoids 

 {PI. XIV. f. 9-1.2) having, like it, a peripetalous and lateral fasciole and the 

 peculiar structure of the ambulacral petals of the genus, not limited, however, 

 to the anterior ambulacra, but extending to all the petals. The flat test {PI. 

 XIV. f. 12) is also unlike what has thus far been found to be the shape of 

 young in other Spatangoids (Moira, Echinocardium, Spatangus), and further 

 material may yet prove this to be the young of an undescribed Spatangoid, 



