132 HAWAIIAN AND OTHER PACIFIC ECHINI. 



Echinosigra. 



Mortensen, 1907. Ixgolf Ech., pt. 2, p. 68, 82. 



Although Mortensen considers the structure of the bivium as indicating 

 that these are among "the more primitive Pourtalesiae," I am inclined to con- 

 sider them (as he has elsewhere expressed it) "an extreme development, the 

 ultimate end of that branch of the great Echinoid genealogical tree." The 

 bivium, it is true, is not so specialized as in some other members of the family 

 but it is scarcely primitive and could even be interpreted as a reversion. The 

 genus contains only two species of which I have seen neither. 



Key to the Species of Echinosigra. 



Xeck short, its least width nearly .20 of test-length phiale. 



\oc-k long, its least width about .10 of test-length paradoxa. 



Echinosigra phiale. 



Pourtalesia phiale (? Wyville Thomson, 1873. Depths of the Sea, p. 90. 1874. Porcupine Ech , 



p. 749). A. Agassiz, 1881. Challenger Ech., p. 138. 

 Echinosigra phiale Mortensen, 1907. Ingolf Ech., pt. 2, p. 68, 82. 



There can be little doubt that Wyville Thomson and Agassiz had different 

 species in hand when each wrote, but as Thomson's specimens are no longer 

 extant and it is impossible now to determine what his specimens were, I agree 

 with Mortensen that the species described and figured by Agassiz is best con- 

 sidered the true phiale. Originally taken by the Challenger in the Antarctic 

 Ocean at a depth of 1975 fms., it has since been taken by the Ixgolf south and 

 west of Iceland at lesser depths (845-1300 fms.) and by the Gauss in the Antarc- 

 tic Ocean again at 1631 fms. Mortensen has compared the Ingolf and Gauss 

 specimens and vouches for their identity. 



Echinosigra paradoxa. 



Pourtalesia paradoxa Mortensen, 1905. \"n\. Mod f. 1906, p. 203. 

 Echinosigra paradoxa Mortensen, 1907. Ingolf Ech., pt. 2, p. 72. B2 



Judging from Wyville Thomson's figures one might believe that this remark- 

 able form was the one to which he gave the name phiale but there is now do way 

 of deciding the question. The Ingolf secured half a dozen specimens of para- 

 doxa southwest of Iceland at a depth of 843-912 fms. 



