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PROCEEDINGS OF THE NATIONAL MUSEUM 



VOL. 81 



sponge was growing on a macerated dictyonine hexactinellid 

 skeleton. 



Description. — Shape, encrusting. Size, 8 mm thick, 3 hy 6 cm 

 in area. Consistency, very fragile. Color in life, drab with a dis- 

 tinct tinge of orange; dry, dull, drab. Oscules and pores, not evi- 

 dent. Surface, superficially wavy, the ridges about 2 mm high and 

 3 to 4 mm from crest to crest. 



Ectosomal specialization vague, but probably to be characterized 

 as a dermal membrane. Endosomal structure, " crumb-of-bread," 

 with the spicules in complete confusion. 



Principal spicules, styles, usually smooth, but occasionally with a 

 few large spines (fig. 58. ^) ; size, 18/a by 340jli to 33/a by 415/x. In- 



FiGURB 58. — Jia jia de Laubenfels : F, G, X 1,333 ; others, X300 



terstitial spicules, tylostyles (fig. 58, A) ; size, about 5/a by SZOfi, 

 First microscleres, palmate isochelas (fig. 58, C, G) -, length, 24ju, to 

 29/i ; they are quite markedly contorted. Second microscleres, toxas 

 (fig. 58, />) ; length, 145/x to 190^. Third microscleres, J-shaped (fig. 

 58, E, F) ; the length from the large end to the bend is between 16|a 

 and 17/x, with very little variation. The entire microsclere if 

 straightened out would probably be 30/x to 35^ long. At the thicker, 

 longer branch they reach a diameter of about 0.0015 mm and termi- 

 nate in a rounded shape like a microstyle. Throughout their length 

 they grow progressively finer, so that even with oil immersion it is 

 impossible to see exactly where they end, the slender branch growing 

 finer and finer down to the limit of vision. This is most extraordi- 

 nary. They are very nearly in one plane, not contort. 



