290 ERYLUS ROTUXDrs. 



Mr. Kirkpatrick, clearlj- shows, that tliis species also differs from Erylus sollasii. 

 The chief differences between the two are the presence of asters 100 fi 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, figs. 14, 18, 24, 33-35; Plate 7, figs. 22-30, .57-73; Plate 8, fig. 13. 



typica, VAT. nov. 

 Plate 5, figs. 1-4, 11-17, 30; Plate 6, figs. 15-17, 25, 27, 30-32; Plate 7, figs. 16-21, 46-56. 



cidaris, var. nov. 

 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 specimens represent seven distinct forms which fall into 

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

 sesses remarkable rhabd-clusters reseml)ling certain Cidaridae in appearance, 

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

 of these spicules, differ in respect to their microrhalxls, the.se being very much 

 larger in one of them than in the other. The former I name megarhahda: for 

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

 typica. 



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

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

 lated below : — 



Erylus rolundus 



var. megarhabda 



form A: 2 specimens from the south coast of Molokai (Sta- 

 tion 3849); 

 " B: 1 specimen from the coast of Kauai (Station 3982); 

 var. typica 



form A: 4 specimens from the south coast of Molokai (Station 

 3849), 

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

 (Station 4024); 



