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PROCEEDINGS OP THE NATIONAL MUSEUM 



VOL. 81 



is thicker than 15 mm. Pores, Wjx to 75jli in diameter; abundant 

 over the entire surface. Surface, superficially pilose, with spicules. 

 Ectosomal specialization, vague. There seem to be no special 

 ectosomal spicules, unless those rated as interstitial may be so re- 

 garded; their location is definitely down amidst the endosomal 

 structures, however. Endosomal structure, predominantly proto- 

 plasmic, with ascending plumose columns of smooth styles, sparsely 

 echinated by small acanthostyles. Numerous slender subtylostyles 

 are scattered in the flesh and protrude from the surface. Histologi- 

 cal details: The abundant flagellate chambers are about 30/i in 



F G H 



FiGUKK 55. — Mictuciunu microjoanna tie Laubenfels : A-E, X300; others, X 1,333 



diameter. Ascending fibers, about 300;u, in diameter, containing 

 little spongin. 



Interstitial spicules, subtylostyles (fig. 55, B) ; size, 3/x by 205/x to 

 4)Lt b}'' 260/A. Coring spicules, smooth styles (fig. 55, A) ; size, 20/a 

 by 280/A to 27/x by 330/^. Echinating spicules, acanthostyles (fig. 

 55, O) ; size, 5)u, by 85fi to lOfi by lOO/x. First microscleres, palmate 

 isochelas (fig. 55, F-G) ; length, 12ja to 16/x. Second microscleres, 

 toxas (fig. 55, Z>) ; length 60/* by 140/*. Third microscleres, pecul- 

 iar sigmoid siliceous bodies present in small numbers in boiled-out 

 samples of the specimen collected in 1926 (fig. 55, H) ; they may 

 not be proper and may have some connection with the chelas, but 

 satisfactory explanation of them is not now at hand. 



Remarhs. — There is a group of sponges, characterized, among other 

 features, by fibers cored with smooth monaxones and echinated by 



