194 



GEODIA MEDIA. 



Geodia media Bowerbank. 

 Plate 16, figs. 1-21; Plate 17, figs. 1-22 



Proe. Zool. soc. London, 1873, p. 13, pi. 2, figs. 24-29. 

 Si/nops (?) media Sollas, Rept. voy. "Challenger," 1888, 25, p. 266. 

 Siflonops media (Bowerbank) Lendenfeld, Tierrcich, 1903, 19, p. 103. 



There are in the "Albatross" collection eight specimens in spirit from 

 Panama, which, as a comparison with a part of the type of Geodia media Bower- 

 bank in the British Museum, kindly placed at my disposal for examination by 

 Mr. Kirkpatrick, shows, belong to this species. 



One of the eight "Albatross" specimens is digitate, the others are, Hke 

 Bowerbank's type, irregularly massive. The former differs slightly in regard 

 to the dimensions of its spicules and the character of its canal-system from the 

 latter. As will be seen from the description given below, these differences are 

 not sufficient, however, for the establishment of subspecies or varieties I con- 

 sider them as two different forms of one species. 



Shape and size. Of the seven specimens of the massive form one, the 

 largest, is fairly complete, the other six are more or less fragmentary. The 

 complete massive specimen (Plate 16, fig. 16) is an irregular mass 85 mm. long, 

 41 mm. broad, and 29 mm. high. It is attached at several points. Between 

 these points of attachment the lower surface is considerably raised, and thus forms 

 the roof of rather high tunnels which undermine the sponge. On the upper 

 side fiat-bottomed depressions, irregular in outline and 9-21 mm. in diameter, 

 are observed. These are surrounded by conspicuous elevated borders, which 

 here and there rise to form higher, rounded protuberances. The surfaces of the 

 depressions are occupied by small, shallow pits, the centres of which are about 

 1 mm. apart. These pits are separated from each other by minute ridges which 

 form a network. The convex parts of the upper side and the unattached parts 

 of the lower side are smooth. Here and there a few spicules protrude beyond 

 the surface, but there is nowhere a trace of a true spicule-fur. Larger open- 

 ings, oscula or openings of uniporal cortical canals, are absent. The smaller, 

 fragmentary massive specimens are quite similar to the large one. They 

 measure 26 38 mm. in maximum diameter. One has depressed pit-bearing 

 areas, up to 35 mm. long. 



The single specimen of the digitate form (Plate 16, fig. 17) is a curved irregu- 

 lar cylinder, 65 mm. long, 6-12 mm. thick, and attached at several points 

 along one side. Its transverse section is throughout more or less circular. The 

 surface is smooth, slightly undulating, and destitute of a spicule-fur. There 



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