128 HAWAIIAN AND OTHER PACIFIC ECHINI. 



Ceratophysa rosea. 



Pourtalesia rosea A. Agassiz, 1879. Proc. Amer. Acad., 14, p. 206. 

 Ceratophysa rosea Pomel, 1883. Class. Meth. Ech., p. 40. 



This species, the affinities of which are really quite uncertain, was taken 

 in mid-Pacific, by the Challenger at the notable depth of 2600 fms., a trifle 

 over three miles. As only fragments were collected, the size and form are 

 unknown. 



Helgocystis. 



Mortensen, 1907. Ingolf Ech., pt. 2, p. 82. 

 Type, Pourtalesia carinata A. Agassiz, 1879. Proc. Amer. Acad., 14, p. 205. 



Here again we have a monotypic genus, with the constituent species known 

 only from fragmentary specimens taken by the Challenger at great depths 

 in the southern Indian (1600 fms.) and Antarctic (1950 fms.) Oceans and off 

 the coast of Chile, (2225 fms.). 



Pourtalesia. 



A. Agassiz, 1869. Bull. M. C. Z., 1, p. 272. 

 Type, Pourtalesia miranda A. Agassiz, 1869. hoc. cit. 



Although monotypic when established, deep-sea exploration has added to 

 this genus nearly a dozen nominal species. Under Mortensen's careful study, 

 and revision, five species have been grouped in other genera, leaving seven to be 

 considered here. Of these, I am convinced that wandeli Mortensen is synony- 

 mous with miranda A. Agassiz. Mortensen himself suggests they are identi- 

 cal. His hesitation in identifying his specimens as miranda seems to have been 

 due to expecting too great accuracy of detail in Roetter's drawings of fifty years 

 ago. Mortensen is no doubt correct in estimating that the holotype of iniranda 

 (which is no longer in existence) was 18-20 mm. long. I have compared a speci- 

 men of wandeli from West Greenland, identified by Mortensen, with one of 

 miranda from Grenada, identified by Mr. Agassiz, and find no difference. The 

 two forms are therefore treated as synonymous. I am tempted to follow the same 

 course with laguncula A. Agassiz and tan»cri A. Agassiz. and perhaps witli alcocki 

 Koehler, for these three species are very nearly related, and the differences 

 between them (as shown by the key below) are trivial. However as specific 

 lines are very hard to draw in the genus and my material (except of la<iuncula) 

 is scanty, I recognize six species for the present. The form of the test is rather 



