186 HAWAIIAN AND OTHER PACIFIC ECHINI. 



Araeosoma hystrix A. Ag. and CI. 



Calveria hystrix Carpenter and Jeffreys, 1871. Proc, Roy. Soc. London, XIX, p. 154 

 Calveria hystrix Wyv. Thomson, 1872. Proc. Roy. Soc. London, XX, p. 494, 

 (Not Calveria hystrix Carpenter, Jeffreys and Thomson, 1870, Proc. Roy. Soc. London, XVIII, p. 445.) 

 Asthenosoma hystrix A. Agassiz, 1872. Rev. Ech. Pt. I, p. 93. 



North Atlantic ; 100-1000 fathoms. 



In confirming Agassiz's rejection of Calveria (Pan. Deep-Sea Ech., p. 84), 

 Bather has pointed out (Ann. Mag. Nat. Hist. (7) XVII, p. 249) that the 

 specific name (hystrix) having been rejected as a homonym, it should not be 

 used for this species. This may be correct nomenclature, but we cannot see 

 what is gained by any change from the universally used specific name. 



Araeosoma pyrochloa A. Ag. and CI. 



Asthenosoma pyrochloa A. Agassiz and Clark, 1907. Bull. M. C. Z., LI. p. 118. 



Plates 66, figs. 1-J^; 78-80. 



Although this species bears a close resemblance to the preceding, the 

 differences pointed out on p. 175 seem to be constant, and warrant the rec- 

 ognition of this form as the North Pacific representative of A. hystrix. The 

 small size of the actinostome is particularly worthy of note. The diameter 

 of the specimen figured on Plates 78 and 79 is 196 mm. From the ambitus 

 to the abactinal system there are in each column 35 interambulacral plates, 

 each carrying from one to four primary tubercles arranged in four or five 

 irregular vertical rows. On the actinal side of the test there are 25 plates in 

 each half-interambulacrum, and each plate carries two to four primary tuber- 

 cles, one of which is always at the extreme ambulacral end of the plate. A 

 very complete marginal series is thus formed, but the series near the median 

 line is much less regular. The rest of the interambulacral plates are covered 

 with numerous secondaries and miliaries. The plates increase in height 

 somewhat as they pass from the ambitus towards the abactinal system and 

 actinostome. On the abactinal side of the test (PI. 78) there are in each 

 column 48 ambulacral plates, increasing very gradually in height from the 

 ambitus to the abactinal system. Each plate carries one or two primary 

 tubercles, which form two very irregular vertical rows on each half- 

 ambulacrum. Excepting the extreme outer end, the ambulacral plates are 

 covered with a series of large miliaries. Towards the ambitus, on the 

 abactinal side of the test, the poriferous zone is equal in width to half that 



