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THE SPONGES. 



161 



The style is the chief spicule in the radial fibres, projecting obliquely 

 upward and outward from the fibre (Plate 25, Pig. 2). At the end of the 

 fibre styles project beyond the surface forming a tuft. The common size in 

 the radial fibre is about 360 /x x 18^ although somewhat smaller ones and 

 larger ones up to 730 /x x 20 /x are present. 



3. Small style (Plate 19, Fig. 4; Plate 25, Fig. 2), commonly bent 

 near the base. Rounded base of spicule may be either not attenuated or 

 attenuated. Occasionally the base is pointed, the spicule thus becoming an 

 oxea. Common size, about 170 /x x 8 /x. 



The spicules project out at right angles from the longitudinal fibres and 

 connectives, and from the deeper parts of the radial fibres. They are thus 

 true echinating spicules, but not nearly so conspicuous as in the Ectyoninae. 

 They are not present in great abundance anywhere, and transitions between 

 them and the larger styles occur. 



Comparative. The species just described is close to the type of the genus^ 

 Aidetta s?j cinalaria Schm. (0. Schmidt, 1870, p. 45, Taf. IV. Fig. 5) from the 

 Florida coast, a specimen of which in the Museum of Comparative Zoology 

 I have examined. In A. sycimdaria the terminal branches are slenderer than 

 in my species, and the wall much thinner. The wall is so thin that the 

 superficial radiating tufts of spicules arise directly from the longitudinal fibres ; 

 there being no radial fibres, as in A. clendrophora. In the specimen exam- 

 ined, a typical terminal branch measures 2.5 mm. in diameter, and the wall 

 is 0.5 mm. thick. The two species contain the same classes of spicules. 



In habitus A. dendrophora exhibits a point of resemblance to A. aurantiaca 

 Dendy (Dendy, 1889, p. 92, Plate V. Fig. 13) in that fusion occurs between 

 the lateral surf aces of the terminal branches. But the fusion is slight in my 

 species, whereas in Dendy's the fused branches form "lamellae like pan- 



pipes 





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The two species differ markedly as regards the skeleton. 



Th 



e 



lateral fusion of the branches is carried very far in what seems to be the 

 first Aidetta described, viz. : Spongia lyrata (Esper. Fortsetz, II. 42, tab. LXVII. 

 Figs. 1, 2) from Ceylon. Esper' s figures and the account of the skeleton 

 given by Ehlers (1870, pp. 23, 31) indicate that this sponge is an Aidetta. 

 Ehlers provisionally places the sponge, which has styles and oxeas, in 

 Easpcdgella Schm. Lamarck (1813, p. 382), referring to Esper's sponge, 

 says he has a specimen in his cabinet from the collection of M. Turgot, and 

 gives with a query the Indian Ocean as the locality. 



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