NO. 5 CLARK : ECHINI OF WARMER EASTERN PACIFIC 231 



are uniformly more or less coral red in rather noticeable contrast to the 

 older spines; this is particularly striking if the spine is entirely free from 

 bryozoa or other incrustations. On the whole the coloration and general 

 appearance of panamensis is remarkably uniform and makes the species 

 easy to recognize. 



Distribution. — The most striking fact about the distribution of this 

 Cidarid is that it has not yet been taken at Panama or anj^where else on 

 the coast of North or Central America. The original specimens were from 

 the vicinity of Cocos Island, and from 85-112 fms off Galera Point, 

 Ecuador. The Velero material is all from Cocos Island and vicinity, where 

 this handsome urchin is notably common in 30-50 fms, or from the 

 Galapagos Islands where it was taken at eight stations in depths of 30-150 

 fms, chiefly in the vicinity of Albemarle Island. The station numbers are: 

 143-34, 147-34, 155-34, 171-34, 183-34, 190-34, 324-35, 325-35, 772-38, 

 773-38, 780-38 and 810-38. 



Type.— M.C.Z. no. 327 (Cotype). 



Type locality. — "Cocos Island and Galera Point, Ecuador." 



Depth.— ZOASQ fms. 



Specimens examined. — 84 specimens from 12 stations. 



Hesperocidaris perplexa (H. L. Clark) 



Plate 36, Fig. 3 



Tretocidaris perplexa H. L. Clark, 1907, p. 205; pi. 6, figs. 1, 2; pi. 7, 



figs. 1-4. 

 Hesperocidaris perplexa Mortensen, 1928, p. 421. 



Only five specimens of this near relative to panamensis were known 

 hitherto, so that the large series of nearly 500 specimens in the Velero 

 collections contribute all the information needed to verify the authenticity 

 of the species and reveal such diversity as it shows. The specimens range 

 from 5 mm in test diameter, with spines scarcely 5 mm long to large adults 

 with the test 43 mm in diameter and 25 mm high, with primary spines 

 35-43 mm long. The flattening of the distal part of the large primary 

 spines, on which Mortensen lays great stress, is not evident until the test 

 is 30 mm or more in diameter and even then it is not conspicuous in most 

 specimens. In the most extreme case at hand, the test is about 37 mm in 

 diameter and the longest primaries are about the same ; the tips of ten or 

 a dozen of these, at or above ambitus, are 3 to 5 mm wide ; the distal half 

 of each of these widened spines is very rough with crowded, more or less 

 sharp tubercles. In most specimens the primaiy spines are nearly cylindri- 



