HAWAIIAN AND OTHER PACIFIC ECHINI. 



Collected by the U. S. Fish Commission Steamer "Albatross," Commander 

 Chauncey Thomas, U. S. N., Commanding in 1902, and Lieut. Com- 

 mander L. M. Garrett, U. S. N., Commanding in 1906. 



ECHINOTHURIDiE Wyv. Thorn. 

 Some Anatomical Features. 

 Plates 60-63. 



ALTnouGn various writers 1 have discussed the anatomy of the Echino- 

 thuridoB in more or less detail, and some have published figures to illustrate 

 certain anatomical peculiarities, it has seemed to be desirable to give a few- 

 figures showing the general arrangement of the alimentary canal and the 

 lantern in some of the species, whose anatomy has not hitherto been figured. 

 As our investigations have led us to believe that the Echinothuridas and 

 Diadematidae are nearly related families, we have also added a few figures 

 showing the anatomy of several species of Diadematidas. 



A comparison of the figures given on Plates 62 and 63 shows that the 

 genera of Echinothuridae differ not a little among themselves in the details 

 of their structure. It is, nevertheless, instructive to compare these figures 

 with those of the genera of Diadematidae given on Plates 60 and 61. The 

 oesophagus, for example, is shortest in Echinothrix (PL 60, fig. 3), some- 

 what longer in Micropyga (PL 61, fig. i) and Phormosoma (PL 62, fig. 2), 

 much longer in Echinosoma and Sperosoma (PL 62, figs. 3, 4), and longest 

 in Asthenosoma (PI. 62, fig. 1) and Astropyga (PL 61, fig. 3). 



The alimentary canal of Phormosoma is remarkably different from 

 that of Asthenosoma (compare figs. 1 and 2, PI. 62), but it is interesting 

 to note that that of Echinosoma (PL 62, fig. 3) is quite intermediate. 



1 Wyville Thomson, 1S74: "Porcupine" Echinoidea, Trans. Roy. Soc. London, 164, pt. 2, Pis. 

 LXIII-LXVII. A. Agassiz, 1881 : " Challenger " Echinoidea, Pis. XII, XIV, XVIII". Paul and 

 Fritz Sarasin, 1888: Ergeb. Nat. Forsch. Ceylon, I, Pis. XII-XVII. Kciehler, 189S : "Hirondelle" 

 Echinides, Pis. IV and IX. Schurig, 1906 : Wiss. Ergeb. d. Deutsch. Tiefsee-Exp. 5, lfg. 3, 

 Pis. LI-LIV. 



