NO. 5 CLARK: ECHINI OF WARMER EASTERN PACIFIC 325 



Encope grandis L. Agassiz 

 Plate 53, Fig. 42 



Encope grandis L. Agassiz, 1841, p. 57, pi. 6. 



This easily recognized sea-urchin, or key-hole urchin, is very abundant 

 in the Gulf of California and the Velero has brought home no fewer than 

 1,222 specimens, ranging in size from 40 x 40 mm to the big adults exceed- 

 ing 100 mm in length with a breadth usually somewhat less but often 

 somewhat greater. The largest specimen in the collection is 116 mm long 

 by 111 mm wide and 16 mm thick, while another individual from the 

 same station (689-37) is 111 mm long by 115 mm wide and 16 mm 

 thick. The percentage of the total weight which the skeleton makes is 

 very great but has not been worked out. Although the coarse and heavy 

 build makes the specimens unmistakable, there is extraordinary diversity 

 in the posterior unpaired lunule, which ranges from nearly circular to a 

 long and narrow slit. The most striking case is a specimen 100 x 90 mm 

 in which the lunule is circular and only 3 mm in diameter. This is such an 

 extreme case it is probably pathological. At the other extreme is an indi- 

 vidual with the lunule 20 mm long but only 6 mm wide. There is appar- 

 ently no correlation between size or weight of the individual and the size 

 of the lunule. Thus a specimen 100 x 105 mm has the lunule 17x10 mm 

 but another specimen from the same lot, 92 x 92 mm has the lunule 33 x 16 

 mm. The color is dull purple, approaching black, or some shade of brown, 

 ranging from fawn color in some young individuals to very deep blackish 

 brown in adults. The margmal area is often darker than the center and the 

 lower surface is lighter than the upper, often markedly so. But there is no 

 distinctive feature in the coloration. 



Distribution. — The Velero took grandis at only 10 fathoms, all in the 

 Gulf of California, mostly along shore, but occasionally it was dredged in 

 from 1 to 10 fms. The scarcity of young individuals or even small adults is 

 striking but may be associated with the fact that all the material was col- 

 lected between January 30 and March 23. Perhaps collections made in 

 summer or early fall would show a larger number of young. 



Type. — (Germany?) 



Type locality. — ". . . . provient probablement des Antilles." 



Depth. — Shore to 10 fms. 



Specimens taken. — 1,222 specimens from 10 stations. 



