142 THE SPONGES OF THE WEST-CENTRAL PACIFIC 



<-> d 



Text Figure No. 90. Spicules of Clathria abietina, X 781. A: Style. B: Acanthostyle. 

 C: Two of the toxas. D: Palmate isochela, side view. 



extremely elaborate structure. The pores are about 150 ll in diameter and 

 about 400 fx apart, center to center. The oscules are 2 mm in diameter and 

 are about 2 to 7 cm apart. 



The ectosome in general is merely fleshy, as characteristic of the genus 

 Clathria, but the tips of the conules are packed with spicules, which suggests 

 the genus Thalysias. These spicules are, however, like those in the endosome 

 and not a special type. They are not substylotylote or tylostylote ; hence 

 the genus Clathria seems to be warranted. The endosome is a definite fibro- 

 reticulation with fibers, 50 \x in diameter, outlining rounded meshes, 100 ii 

 to 300 jx in diameter. These fibers are packed with spicules and also are 

 echinated. 



The skeleton is characterized principally by megascleres which are 

 smooth styles, 6 p, by 200 /a. In addition, there are occasionally echinating 

 acanthostyles, 3 /x by 54 p. in dimensions. The spines are small. The micro- 

 scleres include abundant toxas of rather typical shape, varying from 55 ja 

 to 140 fi in length, and there are small palmate isochelas, only 10 ii long, with 

 very narrow shovels. 



Identification of this sponge is quite dubious and points up the diffi- 

 culty of discriminating between Clathria and Thalysias. Lamarck, 1814, 

 page 450, described a sponge from unknown locality as Spongia abietina 

 Topsent, 1932, page 115, redescribed Lamarck's specimen, and assigned it 

 to the genus Raphidophlus, which is a complete junior synonym of Thalysias. 

 This specimen from Truk (dubiously) is identified with abietina, because of 

 the great resemblance of external form and because the spicules differ only 

 a little. Yet inasmuch as they differ at all, the Truk specimen is a Clathria 

 rather than a Thalysias. Furthermore, since Lamarck's specimens were dry, 

 no data were available as to the presence or absence of the peculiar red sub- 

 dermal layer. It is decidedly possible that the specimen here discussed, No. 

 M. 472, is not only a different species from abietina but even a different 

 genus. It is obvious that a complete revision of the genera Thalysias and 

 Clathria is needed and should be based (if at all possible) upon study of 

 actual type specimens. Under such circumstances it is sometimes advisable 

 to give a new name to a possibly new species, but there are so very many 

 names already cluttering up the literature of these two genera that such 

 action is not here taken. 



