240 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



other species) but are frequently quite plainly outlined in some shade darker than 

 the test, though they are often very indistinct. The ambulacral and interambula- 

 cral areas are nearly equal in width at the ambitus but the interambulacra may be 

 somewhat broader. The pores on the abactinal surface are arranged in a double 

 series on each side of the ambulacrum but the outer series contains fifty per cent 

 more pores than the inner, and a quincunx arrangement is seldom visible. There 

 are very few large tubercles on the abactinal surface (about 35 in the largest speci- 

 men), and relatively few actinally ; the latter are confined to the plates near the 

 ambitus. The greater part of the actinal surface, especially about the actinostome, 

 is closely covered with small tubercles of more or less uniform size, giving an 

 appearance not wholly unlike Chaetodiadema ; this is most marked in large indi- 

 viduals. The specimens taken range from 20 to 220 mm. in diameter. 

 Station 3824. Off Lae-o Ka Laau Light, Molokai, 222-498 fathoms. 



3865. Pailolo Channel, between Maui and Molokai, 256-283 fathoms. 

 " 3979. Off Modu Manu, 222-387 fathoms. 



3988. Off Hanamaulu, Kauai, 165-469 fathoms. 

 " 4015. Off Hanamaulu, Kauai, 318-362 fathoms. 

 4021. Off Hanamaulu, Kauai, 286-399 fathoms. 

 4025. Off Mokuaeae Point, Kauai, 275-368 fathoms. 

 " 4036. Off Kawaihae Light, W. coast of Hawaii, 687-692 fathoms. 

 4089. Off Mokuhooniki Islet, Pailolo Channel, 297-306 fathoms. 

 4096. Off Mokuhooniki Islet, Pailolo Channel, 272-286 fathoms. 

 " 4112. Off Lae-o Ka Laau Light, Molokai, 433-447 fathoms. 

 " 4117. Off Kahuku Point, Oahu, 253-282 fathoms. 



4130. Off Hanamaulu, Kauai, 283-309 fathoms. 



" 4131. Off Hanamaulu, Kauai, 257-309 fathoms. 



4134. Off Hanamaulu, Kauai, 225-324 fathoms. 



4136. Off Hanamaulu, Kauai, 294-352 fathoms. 



" 4137. Off Hanamaulu, Kauai, 411-476 fathoms. 



Thirty-nine specimens. 



ECHINOMETRIDAE Gray. 



Heterocentrotus mammillatus Br. 



Cidaris mammillata Klein, 1734. Nat. disp. Ech. p. 19 ; Plate 6, Figs. A, B. 

 Heterocentrotus mammillatus Brandt, 1835. Prod. Desc. Anim., p. 266. 



All the specimens of Heterocentrotus in the collection are referable to this 

 species. 



Laysan Island, and Puako Bay, Hawaii. 

 Twenty-four specimens. 



Colobocentrotus Quoyi Br. 



Echinus Quoy de Blainville, 1825. Diet. Sci. Nat. 37, p. 96. 

 Colobocentrotus Quoyi Brandt, 1835. Prod. Desc. Anim., p. 267. 

 A large series of Colobocentrotus was taken but all are referable to this single 

 species, and show little variation. 



