IS SIDONOPS CAI.IFORNICA. 



Of the eighteen species, three have been previously described, and fifteen 

 are new. In one of the previously known species two new varieties are 

 described. 



SIDONOPS SoLL.w. 



Among the megascleres are regular triaenes. The tetraxon megascleres 

 are confined to the superficial part of the sponge and are arranged radially. The 

 dermal microscleres are asters. The afferents are cribriporal; the efTerents 

 uniporal. 



There are twenty-three specimens of Sidonops in the collection made by 

 the "Albatross." These belong to four species; all are new, and one is divided 

 into three varieties. 



Sidonops californica, sp. nov. 

 Plate 5, fi,?.s. 1-37. 



Shape and size. The two specimens in the collection were obtained off 

 Lower California, and to this locality the specific name refers. They are some- 

 what fragmentar}'. Both are elongate tuberous, somewhat finger shaped. The 

 larger (Plate 5, fig. 6) is 2-4 mm. long and 6-10 mm. broad, the other measures 

 18x7-9 mm. Both appear to be digitate processes, broken ofT from a larger 

 mass; the smaller one was attached at one side. The surface is undulating, 

 and no trace of a spicule-fur can be made out with the unassisted eye. The 

 microscopic investigation of radial sections, however, shows that minute dermal 

 styles protrude slightly beyond it. In several places circular efferent pores, 

 100-300 n wide, arc observed. These pores are not numerous. They congre- 

 gate in groups, one of which is situated on the rounded tip of the larger speci- 

 men. Parts of the surface are covered with a thin desmacidonid sponge-crust. 



The colour (in spirit) is yellowish white, slightly darker in the interior than 

 on the surface. 



The cortex is about 500 /i thick and composed of a sterraster-armour. 



Canal-system. Radial canals, 100 300 /< wide, traverse the sterraster- 

 armour. Most of these are covered distally with sieve-membranes, the pores 

 of which are oval, 30-100 /n wide, and occasionally so close together as to be 

 separated only by slender threads. These threads exhibit, when observed with 

 higher powers, a longitudinal striation. The radial cortical canals not covered 

 by such sieves, which I consider as efferents, form the groups above described. 

 The remainder of the surface is occupied by the afferent, cribriporal, cortical 



