Verrill, JVbtes on Radiata. 375 



Echinometra Van Brunti a. Ag. ; VerrUi, op. cit., p. 309. 

 Common at La Paz. 



Tripneustes depressns A. Ag., BuUetin M. c. z., p. 24, i863. 



Large and ventricose, slightly concave beneath, regularly arched 

 above, the outline in a vertical view nearly circular, with the ambu- 

 lacral zones a little swollen. Peristome larger m proportion to the 

 diameter of the test than in T. ventricosus. Primary tubercles of 

 interambulacra less numerous, especially in the vertical series, owing 

 to the greater vertical width of the plates ; secondary tubercles few 

 and small, miliaries very numerous and minute. Tubercles of the am- 

 bulacra similar in size and appearance. Diameter of test 4-9 ; height 

 2-85; diameter of peristome, not including cuts, 1*15: of abactinal 

 area "70; width of ambulacral zones at circumference 1*30; of inter- 

 ambulacral 1*70. 



This species is closely allied to T. ventricosus of the West Indies. 

 The only reliable characters for separating it, that I have been able 

 to find, are the greater relative size of the buccal opening, and the 

 fewer primary tubercles, with much less numerous secondary ones, 

 which, combined with the smallness of the miliaries, gives the sur- 

 face a less closely tuberculated appearance. 



It was characterized by Mr. A. Agassiz, only as follows : — " There 

 is in the collection of the Smithsonian, a species from Guayamas, 

 T. depressus A. Ag., closely allied to T. ventricosus, which differs 

 from it in the flatness of the test, the large and uniform size of the 

 tubercles, and the stoutness of its spines." 



The spines in our specimen are removed, but in form it is less de- 

 pressed than many specimens of T. ventricosus, and the primary tu- 

 bercles are scarcely larger. 



EllCOpe grandis Agassiz, Monog. Scut., p. 37, Tab. 6. 



A large and fine specimen, which was certainly collected at La Paz, 

 came with the collection, thus confirming the Gulf of California na- 

 tivity of this species, which has been erroneously attributed to the 

 West Indies. 



BrissnS obeSUS Verrill, op. cit., p. 316. 



Tliis species is represented only by a single specimen, which agrees 

 well with those originally described. 



Trans. Connecticut Acad., Vol. I. 48 April, 1868. 



