NO. 5 CLARK: ECHINI OF WARMER EASTERN PACIFIC 331 



Encope galapagensis A. H. Clark 

 Plate 57, Figs. 50-51 



Encope micropora galapagensis A. H. Clark, 1946, p. 7. 



One of the most interesting results of the study of the large number of 

 Encopes in the Velero collection was the discovery that the Galapagos 

 form is easily recognizable as a distinct species. The character upon which 

 the subspecies was based is not perfectly constant, for while the test is as a 

 rule equally high both in front of and behind the middle, there is individual 

 diversity which results in many specimens being slightly highest anterior 

 to the middle. Verj' rarely a specimen is highest posteriorly. The most 

 obvious character is the color, commonly an antique or brussels brown 

 above with the margins of the lunules as well as of the test itself dusky 

 purple. The lower side is a dark purple drab, sometimes quite purple, 

 sometimes quite drab. The contrast between the upper and lower surfaces 

 is usually marked. About 10 per cent of the specimens tend to be either 

 grayish with a purple cast or even a rather evident purple. Such specimens 

 show little evidence of the antique brown of normal specimens. The 

 lunules are commonly elongated and relatively narrow, from 2 to 4 times 

 as long as wide, but the anterior lunules are frequently small and more 

 nearly circular. The unpaired lunule is longest and its anterior end is 

 commonly between the tips of the posterior petals, but in some individuals 

 a line between those tips would be entirely anterior to the unpaired lunule. 

 Commonly the test is nearly circular but it is usually a little wider than 

 long when full grown. The margin between the posterior petals is often 

 nearly or quite straight but is commonly more or less convex. 



The smallest specimen at hand is 10 mm in diameter with only the 

 unpaired lunule evident. At 12-15 mm the posterior paired lunules appear 

 as notches in ambulacra 1 and 5, but the notches indicative of the 3 

 anterior lunules are not evident until the young Encope is about 25 mm 

 across. These young are very pale gray brown but at 3 mm the color is 

 more brown and margin of the test is purple as in adults but not markedly 

 so. The largest individuals exceed 130 mm in diameter, the length and 

 breadth about equal or the width greater. At Tagus Cove, Albemarle 

 Island, fine specimens were secured, 152 x 151 mm, and at Academy Bay, 

 Indefatigable Island, specimens 150 x 155 mm were collected. 



Distribution. — This fine Encope was taken only at the Galapagos 

 Islands, from North and South Seymour Islands and Indefatigable, 

 Albemarle, Charles, Hood, and Chatham Islands. 



T^,^^.— U.S.N.M. No. E. 6817. 



Type locality. — Chatham Island, Galapagos. 



Depth.— 2-lZ fms. 



Specimens examined. — 120 specimens from 22 stations. 



