GEODIA AGASSIZII. 



113 



tion, and at first I thought that it was a young G. mesotriaena. A more careful 

 examination showed, however, that it differs from the latter not only by the 

 smaller size of its spicules, which, in view of the small size of its body, would 

 not, by itself, be of any systematic importance, but also by the shape of its 

 mesotriaenes, orthotriaenes, and oxysphaerasters. The mesotriaene-epirhabds 

 are in G. mesotriaena as long as or longer than the clades in G. mesotriaenella, as a 

 rule, they are very considerably shorter. The ortho- or plagio-triaene-clades 

 are in G. mesotriaena nearly straight or somewhat turned upward at the end, in 

 G. mesotriaenella concave towards the rhabdome right up to the tip. The oxy- 

 sphaerasters of G. mesotriaenella have stouter and less spiny rays than those of 

 G. mesotriaena. Geodia mesotriaena differs from G. ovis, by the possession of 

 praeoscular cavities in the interior ; by its spicule-fur being not nearly so highly 

 developed; by having much smaller dermal strongylosphaerasters, and by the 

 absence of the minute anatriaenes and the oxyasters with very stout, regularly 

 conical, sharp-pointed rays, which characterize G. ovis. 



Geodia agassizii, sp. nov. 



Plate 26, figs. 1-21; Plate 27, figs. 1-19; Plate 28, figs. 1-28; Plate 29, figs. 1-17; Plate 30, figs. 1- 

 17; Plate 31, figs. 1-10; Plate 32, figs. 1-46; Plate 33, figs. 1-14; Plate 34, figs. 1-17. 



Cfjdoniiim miUleri L. M. Lambe (iioii Fleming), Trans. Roy. soe. Canada, 1893, 11, p. 36, pi. 4, fig. 2. 



I establish this species for twenty-two specimens obtained at nine different 

 stations on the west coast of North America ; eight at Station 2886, one at Sta- 

 tion 2887, two at Station 2978, one at Station 3088, one at Station 3168, two 

 at Station 4193, four at Station 4199, two at Station 4228, and one at Station 

 4551. 



The reexamination of the sponge determined by L. M. Lambe (loc. cit.) as 

 Cydonium miUleri Fleming in the collection of the Geological Survey of Canada, 

 and which was kindly placed at my disposal for examination, shows that it 

 differs specifically from the typical Geodia (Cydonium) miilleri and is an 

 immature form of the sponges here described. A new species with another 

 specific name must therefore be established for these sponges and Cydonium 

 mulleri Lambe 1893. 



Although much has been written on the variability of sponges, our knowl- 

 edge concerning this subject is still very vague. The results of the examination 

 of the differences between these sponges, given below, throw some light upon it 

 so that greater general interest attaches to this species than to most of the 

 others here described. For this reason I have selected for it the name agassizii. 



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