14 PEOCEEDINGS OF THE NATIONAL MUSEUM vol.81 



studied, all from southern California. The species is abundant at 

 this locality. In September, 1925, I found it on pilings of a wharf 

 at Venice, Calif. The University of Southern California collected 

 it twice in July, 1914, without locality record, at Whites Point (near 

 San Pedro) without date record (U.S.N.M. No. 21407), and on July 

 13, 1923, at Point Vincente (near San Pedro) (U.S.N.M. No. 21402). 

 The species occurs in a variety of situations throughout the lower half 

 of the intertidal zone, seeming to favor situations in the bottom of 

 crevices and where the wave action is strong. It is much infested 

 with other animals, particularly crustaceans. 



Description. — Shape, amorphous. Size, up to about 2 cm thick 

 and 10 cm in diameter. Consistency, mediocre. Color in life and 

 when preserved, white to pale brown. Oscules, oval, scattered, size 

 about 1 by 3 mm. Pores, not superficially evident. My sections 

 show them definitely closed with a distinct pore-membrane about 5/i 

 to 20/i thick. They lead to canals a little more than 100/x. in diameter 

 so probably can be opened to about that size. Surface, superficially 

 smooth, contort, with lumps and ridges several millimeters high. 



Ectosomal specializations, dermal membrane, 5/i, thick; not detach- 

 able, fleshy, contains abundant nuclei. Below it is a zone about 115/* 

 thick devoid of flagellate chambers, containing amoebocytes often 

 elongate and perpendicular to the surface, in a ground substance 

 (collenchyma) appearing noncellular, probably protoplasmic. En- 

 dosomal structure, leuconid, arranged very much as in many of the 

 Demospongias. It is quite remarkable that this calcareous sponge 

 so closely resembles in shape an amorphous noncalcareous sponge. 

 The surface is often ridged, or again it may be merely irregularly 

 lumpy. The oscules are scattered here and there. From them canals 

 meander through the choanosome, all in quite halichondrine fashion. 

 I have found small specimens scarcely more than a centimeter in 

 diameter, and even they had two or three small oscules and none of 

 the characteristic symmetry of the Calcarea. It would be most inter- 

 esting to find still younger forms and trace the earl}^ stages. Histo- 

 logical details (besides those mentioned above) : The flagellate cham- 

 bers are usually oval, extreme measurements about 30/i, to SOju. 



First type of spicules regular tri axons (fig. 6, 6', Z>, and H) ; 

 second type of spicules, sagittal triaxons (fig. 6, F). 



The characteristic spiculation of this species is a confused tangle 

 of two sizes of triaxons, the larger (fig. 6, C) with rays about 40/i 

 by 400/A , the smaller (fig. 6, E) with rays about 13/* by 130/x. Some 

 specimens, including the type specimen, contain numerous interme- 

 diates, but in many specimens the distinction into two different sized 

 ranges is conspicuous. Careful study of many specimens yields the 

 following as supplementary remarks: In two instances I have found 

 a small fourth ray on a spicule (fig. 6, G) ; this item is so rare that 



