22 SIDONOPS CAI.IFORNICA. 



the sterraster surface are covered with spines. In the normal sterrasters each 

 ray bears a terminal verticil of from three to seven conic not very stout spines 

 about 1.5/1 long (Plate 6, figs. 36, 37). 



The two specimens of this species were caught with the tangles at Station 

 2829 on May 1, 1888, off Lower Cahfornia, in 22° 52' N., 109° 55' W., depth 

 56 m. (31 f.); they grew on a rocky bottom; the bottom temperature was 23.4° 

 (74.1° F.). 



Should the uniporality of the efferent cortical canals observed be due merely 

 to a local rubbing off of the superficial parts after cajjture, and should sieve- 

 membranes cover them in the living state, this si:)onge would of coui"se have to 

 be placed in Geodia. Since however no indication of the former presence of 

 sieve-membranes can be discovered at the mouths of the now uniporal efferent 

 cortical canals. I think that these efferents must by nature l)e uniporal and the 

 sponge accordingly placed in Sidonops. 



Among the species of Geodia and Sidonops hitherto described there are only 

 three which at all resemble these sponges: Geodia ramodigitata Carter 1880; 

 the sponge described by Dendy ' as Geodia ramodigitata Carter, which differs 

 however so considerably from Carter's tjpe that I do not think it specifically 

 identical with it; and Synops alba Kieschnick 1896 = Sydonops (recte Sidonops) 

 alba Thiele 1900. From Geodia ramodigitata Carter and also from the species 

 described under this name by Dend}' the above mentioned Californian specimens 

 differ by possessing j)lagiomesoclades often with more or less reduced clades in- 

 stead of the normally develo])ed protriaenes or promesotriaenes, a difference 

 wliicli is in itself, apart from the difference in the superficial part of the canal 

 system, quite sufficient for specific distinction. Sidonops alba (Kieschnick) 

 Thiele ^ is obviously much more closely allied to them. Most of the spicules are 

 identical in shape and not very different in size. The differences between them 

 most important systematically appear to be that Sidonops alba (Kieschnick) 

 Thiele pos.ses.ses small anaclades, which Thiele terms exotyles, whilst the Cali- 

 fornian specimens are destitute of such spicules; that the latter contain minute 

 microam phloxes which are absent in the former; and that the reduction of the 

 mesodade-cladomes is carried considerably further in the former than in the 

 latter. As regards the minute microamphioxes I do not attach very much 

 systematic importance to their presence or absence because it is cjuite possible 



' A. Dcntty. Report on the sponges. Rept. pearl oyster fisheries. 1905, pt. 3, p. S8. 

 ' J. Thiele. Kieselschwamme von Ternate I. Abhandl. Senckenb. gesellsch., 1900, 25, p. 46, pi. 2, 

 fig. 16. 



