160 HAWAIIAN AND OTHER PACIFIC ECHINI. 



Station 5082. Off Omai Saki Light ; 34° 5' N., 137° 59' E. Bott. 

 temp. 37.7°. 662 fathoms. Gn. m., fne. s., glob. 



Station 5084. Off Omai Saki Light ; 34° N., 137° 49' 40" E. Bott. 

 temp. 36.8°. 918 fathoms. Gn. m., fne. s., glob. 



Station 5086. Sagami Bay, Hondo Island, Japan ; 35° 8' 15" N., 

 139° 20' E. Bott. temp. 43.7. 292 fathoms. Gn. m., crs. bk. s. 



Station 5088. Sagami Bay; 35° 11' 25" N., 139° 28' 20" E. Bott. 

 temp. 41.8°. 369-405 fathoms. Gn. m. 



Bathymetrical range, 165-918 fathoms. Extremes of temperature, 

 53.5°-36.8°. 



One hundred and eighty-four specimens. 



ECHINOSOMA. 



Pomel, 1883. Class. Meth. Ech., p. 108. 



Type-species, Phormosoma tenue A. Agassiz, 1879. Proc. Am. Acad., XIV, p. 202. 

 (Including Hygrosoma and Tromikosoma Mortensen.) 



In this genus, the thin and flexible test has the larger spines and areolae 

 on the actinal side, but the contrast with the abactinal is not marked. The 

 hoofs of the actinal primaries are usually large and shining white. The 

 sphoeridia are more or less elongated and are present only on the inner 

 (lower) secondary plate-element. Although it is not difficult to distinguish 

 the genus from the preceding, the species of which it is composed are ex- 

 ceedingly hard to diagnose in such a way as to make them generally 

 recognizable. No less than 11 different forms have been described and 

 named which certainly belong in Echinosoma, but some of these are of 

 doubtful standing. We are unable to distinguish mordeiis de Meij. from 

 tenue A. Ag., or cethiopicum Diid. from hiculentum A. Ag. Doderlein himself 

 says that the latter is "sehr nahe " ccthiojncum, but he distinguislies them 

 by means of the stout, broad-valved, tridentate pedicellariaB which are pres- 

 ent in luculentmn and wanting in mihiojncum. In view of the fact that the 

 presence or absence of a given form of pedicellariie has been shown, in 

 numerous cases, to be a matter of individual diversity onh', we cannot 

 consider a'thlopicum a valid species. Moreover, Impidum. and zcalandia 

 are very near tcnuCy and panamaise and Pefcrsii are very near Krainis. 

 Finally, the line between hoplacantha and hcuJcutum is not as sharp as 

 could bo wished. There seems little reason to doubt that hojilacanthay 



