ENCOPE EMARGINATA. 545 



The interporiferous space in the anterior and posterior petals is nearly of 

 the same width. The poriferous zones are broad, broader than the enclosed 

 area in the posterior and odd petals. The interambulacral lunule is small, 

 though longer than the ambulacral ones, and very variable in shape. The 

 ambulacral hmules are pretty regularly oval ; the odd anterior the smallest ; 

 the anterior pair next in size, and the posterior the largest ; in all the 

 specimens I have seen, they show traces of their mode of formation as mar- 

 ginal cuts, and they are often at a considerable distance from the edge of the 

 test. The internal structure, when compared to one of the other western 

 species, E. micropora, shows a corresponding difference (in the size of the 

 jaws, the dimensions of the walls separating the alimentary canal from the 

 actinal cavity), similar to what has already been alluded to and figured be- 

 tween E. emarginata and E. Michelini. 



This species differs very materially from E. Michelini, in the first place by 

 the relatively much smaller size of the ambulacral petals, which reach a 

 great size in E. Michelini, in the presence, almost universal, of ambulacral 

 lunules ; and, in the second piace, on the actinal side by the position of the 

 anus, and the comparatively larger space enclosed in the broad bulging 

 branches of the ambulacral furrows, which merely diverge from their origin 

 in E. Michelini, and run more parallel towards the edge of the test. 



Gulf of California. 



Encope emarginata 



Echinodiscun emarginatus Leske, 1778, Kl. Add., p. 136. 

 ! Encope emarginata Agass., 1841, Mon. Scut., p. 47, PI. X. 

 (See Part II. p. 325.) 



PL XII. f. 14-24; PL XIP.f. 1-3 ; PL XIP.f. 2-3. 



Brazil ; West Indies. 



Encope grandis 



! Encope grandis Agass., 1840, Cat. Syst. Etyp. 



PL XIII d . f. 5-6. 



The origin of this interesting species Avas not known till General Stone 

 sent some specimens from Guyamas and from other points of the Gulf of 

 California to Professor Agassiz, a short time previous to the publication of 

 the Exchange List of Echini in the Museum Bulletin for 1863. Subsequently 

 it was found again by Captain Pedersen, who sent numerous specimens to the 

 Yale College Museum. It is remarkable for the solidity of the test, the 



