290 



ERYLUS ROTUNDUS. 



Mr. Ivirkpatrick, clearly shows, that this species also differs from Erylus soUasii. 

 The chief differences between the two are the presence of asters 100 /j. in diam- 

 eter and exceedingly irregular aspidasters in E. lendenfeldi, and their absence in 

 E. sollasii. These differences are quite sufficient for specific distinction. 



Erylus rotundus, sp. nov. 

 megarhabda, var. nov. 



Plate 5, figs. 18-23, 32; Plate 6, fig.s. 14, IS, 24, 33-35; Plate 7, figs. 22-30, .57-73; Plate 8, fig. 13. 



typica, var. nov. 



Plate 5, figs. 1-4, 11-17, .30; Plate 6, figs. 1.5-17, 2.5, 27, .30-32; Plate 7, figs. lG-21, 46-56. 



cidaris, var. nov. 



a, 



Plate 5, figs. 5, 26-28, 31; Plate 7, figs. 1-10, 42-45, 75, 76, 79; Plate 8, fig. 14. 



I establish this species for thirteen specimens obtained at five different sta- 

 tions among the Hawaiian Islands. The aspidasters of these sponges are nearly 

 circular in outline and to this the name refers. 



The thirteen sjiecimens represent seven distinct forms which fall into 

 three groups. The latter I consider as varieties. One of these varieties pos- 

 sesses remarkable rhabd-clusters resembhng certain Cidaridae in appearance, 

 hence the varietal name cidaris. The other two varieties, which are destitute 

 of these spicules, differ in respect to their microrhabds, these being very much 

 larger in one of them than in the other. The former I name megarhabda; for 

 the latter, which is the most frequent of the three, I have selected the name 

 typica. 



Two forms belong to the var. megarhabda, four to var. typica, and one to 

 var. cidaris. The number of specimens and the habitat* of each form are tabu- 

 lated below : — 



Erylus rotundus 



var. megarhabda 



^^yty^C *^-3 7 5^ <-~ — fo««-^"- 2 specimens from the south coast of Molokai (Sta- 



tion 3849); 



(^ytOr ^ ^3 Vif ^ B: 1 specimen from the coast of Kauai (Station 3982); 

 var. typica 



4 specimens from the south coast of Molokai (Station 

 3849), 



^^ " B: 3 dark-coloured specimens from the coast of Kauai 

 ^oX.^^^b%^ (Station 4024); 



