186 HAWAIIAN AND OTHER PACIFIC ECHINI. 



the lateroanal fasciole and the slightly sunken petals are all good characters 

 separating the group from the true Periasters. It is possible that Gray's Schiz- 

 aster jukesii should be included in Hypselaster but the deeply sunken petal III 

 seems to prevent such a disposition of that little-known species, and I reluc- 

 tantly place it among the at present unidentifiable forms. It probably belongs 

 in Schizaster. 



Key to the Species of Hypselaster. 



Test very large, length 100 mm. or more; a bare band 2 mm. wide connects the upper 



end of periproct with the peripetalous fasciole maximus. 



Test much smaller; length usually under 60 mm.; no conspicuous bare band between 

 peripetalous fasciole and periproct. 



Test nearly as high anteriorly as at posterior end. 



Petals II and IV only 1.5 times as long as I and V; petal III not twice as long 



as I and V limicolus. 



Petals II and IV twice as long as I and V; petal III 2.5 times as long as I 



and V rotundus. 



Test distinctly higher posteriorly than anteriorly. 



Apical system central or a little anterior fragilis. 



Apical system distinctly posterior. 



Petals 1 and V nearly half as long as II and IV; peristome large (7 by 



3 mm.) kempi. 



Petals I and V much less than half as long as II and IV; peristome small 



(4X2 mm.) brachypetalus. 



Hypselaster maximus. 



Periaster maximus A. Agassiz and Clark, 1907. Bull. M. C. Z., 60, p. 259. 



Plate 154, fig. 18. 



This species is based on a large fragment, of a light brown color, consist- 

 ing of the posterior left-hand quarter, approximately, of the abactinal part of 

 the test, and including the most of petal I and all of petal V. The genital 

 pores are not shown and it is only by inference that the speci< se is placed in 

 Hypselaster. A perfectly bare band, 2 mm. wide and nearly 50 mm. long, runs 

 from the posterior part of the peripetalous fasciole, in the median line, to the 

 periproct, which is present and measures 11 mm. across. Petal V is IS mm. 

 long and 6 mm. wide. The shape of this species was apparently much like 

 that of limicolus and if, by comparison with a Bpecimen of that species 65 mm. 

 long, we calculate its dimensions, we find that the holotype of maximus must 

 have been about 110 mm. long, 105 mm. wide and 05 mm. high. The spines 



