272 HAWAIIAN AND OTHER PACIFIC ECHINI. 



those of horridus, having a very square-cut base and 2 or 3 lateral teeth on each 

 side of the tip of the blade. They measure about .60 mm. long, with the end- 

 tooth some .10 mm., and the base .15 mm. wide. The ophicephalous have the 

 valves about .35 mm. long, besides the loop which may be .08-. 10 more; they 

 are distinctly constricted near the middle. The tridentate are found chiefly on 

 the actinal surface. The valves are .80-1.40 mm. in length, narrow, com- 

 pressed and in contact only at the slightly expanded tip. The valves of the 

 triphyllous pedicellarise are more elongated than usual, measuring .13 by .095 

 mm. Nothing peculiar was noted in regard to the sphseridia and no spicules 

 were found. 



The color is dirty yellowish or pale buff, with the primary spines more or less 

 nearly pure white, and the periproctal plates and secondary spines whitish. 



Although this species is very near some forms of acutus var. norvegicus, the 

 test is much flatter than in any specimens of that variety and the periproct and 

 globiferous pedicellarise are different. 



It was collected by the "Albatross" in February, 1888, at the two follo\\-ing 

 stations : — 



Station 2788. Off Chile; 45° 35' S., 75° 55' W. Bott. temp. 36.9°. 1050 

 fathoms. Gn. m. 



Station 2789. Off Chile; 42° 36' S., 75° 28' W. Bott. temp. 35.9°. 1342 

 fathoms. Bu. m. 



Eighteen specimens. 



Parechinus. 



Mortcnscn, 1903. "Ingolf" Ech., pt. I, p. lOS; 134. 

 Type-species, Cidaris angulosa Leskc, 1778. Add. ad Klein, p. XVII; 2S. 



It is fortunate that ]\Iortcnsen designated no type for his genus Parechinus 

 for had he selected either miliaris or microtuherculalus, the name woukl be simply 

 a synonym of Psammcchinus. As it is those two species must be left in the 

 latter genus (see j). 242) and thus angulosus becomes ipso facto type of 

 Parechinus. Doderlein's name Protocentrotus thus becomes a synonym of 

 Parechinus, having the same type. 



I hav(> placed in (liis genus with angulosus, the closely related aunulatus 

 and the more distantly connected viagcUanicus and Huttoni. While these four 

 species show a similar tendency towards a specialized abactinal system, it is 

 interesting to note that whereas in angulosus, the buccal membrane of which is 

 more or less fully provided with plates. 54 per cent of the specimens have all the 



