264 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 8 



from 47 to 65 per cent of the diameter. Growth changes from 30 mm h. d. 

 to 150 mm are chiefly in the number of secondary and miliary tubercles 

 (and spines, of course). In the young individuals, there are two columns 

 of primary tubercles in the ambulacra and two in the interambulacra, with 

 secondary and miliary tubercles present between them in the interambula- 

 cra in not veiy well-marked series. On the ambulacra there are few 

 tubercles of any importance in the interporiferous area save for one column 

 on each side. In an adult, 100 mm or more in diameter, there are 10-12 

 well-spaced columns of primarj^ tubercles and many well-scattered smaller 

 tubercles in the interambulacra. The ambulacra have undergone a more 

 marked change; 4-6 imperfect columns of primary tubercles occupy the 

 interporiferous area, and the poriferous areas have themselves widened 

 markedly and cany 3 or 4 columns of tubercles mixed with irregularly 

 scattered tube-feet between an inner and outer column of tube-feet which 

 sharply delimit the area. The scattered tube-feet are much more numerous 

 on the inner side of the area than on the outer. As for color, the dry speci- 

 mens are very unattractive, as they were obviously prepared in haste. The 

 test is almost black but with purple tinge more or less evident, and the 

 spines are pale brown or brownish-white. One small adult in alcohol gives 

 a better idea of the color in life. The test is purple, lightest on the porifer- 

 ous areas, darker and duller on the interambulacra and on the interporif- 

 erous areas of the ambulacra. The spines are white in marked contrast to 

 the test. 



Distribution. — The 63 specimens of depressus brought in by the 

 Velero are, with only two exceptions, from outlying islands. The excep- 

 tions are from the shores of Secas Islands, Panama. Of the other 61 speci- 

 mens, 7 are from the Galapagos Islands (Albemarle, Tower, Chatham, 

 Charles, and Gardner), all from along shore except the half grown speci- 

 men from near Gardner Island which was dredged in 12 fms. Of the 

 remaining specimens 43 are from Socorro and 11 from Clarion, all secured 

 by collecting along shore. The type locality is said to be Guaymas, Mexico, 

 but it is notable that neither the Velero nor the Templeton-Crocker 

 Expedition found any Tripneustes in the Gulf of California nor on the 

 Mexican coast. 



Type. — No type. 



Type locality. — Guaymas, Mexico. 



Depth. — Shore to 12 fms. 



Specimens examined. — 63 specimens from 10 stations. 



