THE SPONGES OF THE WEST-CENTRAL PACIFIC 85 



U.S.N.M. No. 22817, My No. N. 024, collected August 18, 1947, by F. M. 

 Bayer and F. C. Zimmerman at Rongerik Atoll from the reef near 

 Latobak Islet. 



The shape is primarily incrusting, but specimen No. M. 373 also pos- 

 sessed a few repent solid branches. The thickness is about 8 to 10 mm and 

 the diameter about 8 cm, but this depends upon environmental circumstances. 

 There is probably indefinite lateral growth. 



The color in life, where the specimen was obviously healthy, was a 

 rather dull purple. This was true also of the endosome. The consistency 

 was softly spongy. 



The surface is punctiform, but the openings are covered with an obvi- 

 ous fine meshed net. The genus Callyspongia especially is distinguished by 

 its peculiar surface. In this species, there is first of all a very neat reticula- 

 tion of fibers about 60 /u. in diameter, outlining meshes which are a little over 

 300 fx in diameter. These meshes are often square, or nearly square, in 

 shape. Within these coarser meshes at the surface are finer ones which are 

 outlined by fibers which are 15 /x to 20 [x in diameter. These smaller openings, 

 frequently square or nearly so, are about 100 /a in diameter. These latter may 

 be regarded as the pores of the sponge. In the species under discussion, ex- 

 halant openings are not conspicuous but do occur and vary from 1 to 6 mm 

 in diameter. In some places there may be as few as only one or two to an 

 incrustation, while in others they are abundant, sometimes in rows. Often 

 each oscule is raised slightly, about 1 or 2 mm above the surrounding surface. 



The ectosome is a peculiar double reticulation described above, the endo- 

 some is a much more commonplace and simple fibro-reticulation. 



The skeleton consists almost entirely of clear spongin fibers as described. 

 These are rather like the ones which are found in the genus Spongia, but 

 here and there, these fibers of Callyspongia are cored with small spicules, 

 all of which are oxeas. In the specimen from Majuro these were only about 

 0.3 fi by 38 /x. In the specimens from Ebon, they are a little larger, ranging 

 from 2 ti by 80 fi to 2 ti by 93 [i. 



Topsent, 1892, page 25, described a sponge as Sclerochalina fistularis 

 from the Red Sea. Burton, 1937, page 21, described a sponge from the 

 Indian Ocean and identified it with fistularis of Topsent but correctly re- 

 ferred it to the genus Callyspongia. The present specimens are identified with 

 these of Topsent and Burton with some hesitation. The species fistularis 

 was supposedly characterized by a peculiarly cartilaginous consistency, not 

 present in these sponges from the western Pacific. But the spicules are 

 about the same size; the surface, with the peculiar type of oscule, is very 

 similar ; and there are so many species already in Callyspongia that it seems 

 inadvisable to add further numbers at the present time. 



