454 PROCEEDINGS OF THE NATIONAL MUSEUM vol.83 



Genus PLACOSPONGIA Gray 



PLACOSPONGIA INTERMEDIA Sollaa 



This species is represented in the collection by U.S.N.M. no. 22201, 

 from the Pacific side, and no. 22233, from the Atlantic side of the 

 Canal Zone. It is moderately common at each end of the canal, 

 forming encrustations about 1 mm tliick on coral or rock. The color 

 in life is orange-ochre, changing to brown or drab in places where it 

 seems to have been adversely affected by the environment. The 

 consistency is friable, hard. The surface is given over to conspicuous 

 polygonal plates separated by cracks only about lOO/x wide. These 

 plates are about 150/i to 350/z thick, and seem to be imperforate. The 

 inhalent and exhalent apertures are presumably in the cracks between 

 them. The endosomal structures are chiefly in confusion, but a few 

 vague tracts about 100/x in diameter may be made out. The mega- 

 scleres are exclusively tylostyles, of which, however, the heads are 

 sometimes so small as to be barely larger than the shaft. These vary 

 in size from about 6/i by 250fx to 8^ by 400^. The dermal cortex 

 is densely packed with sterrasters 20^ by SS/x to 35/i by 50^. Among 

 the other microscleres are small spheres about 8;u in diameter, covered 

 by minute spines; these are young forms of the sterrasters, as shown 

 by the existence of forms intermediate between them. These occur 

 chiefly in the endosome, as do the abundant spirasters Iju by 4^t to 

 2// by 8/i. There are also short spirasters or plesiasters Avith very 

 long spines with a tylote to strongylote modification at the end of each. 

 These range from about 14)u by 18)li to ISju by 20/1. 



Placospongia intermedia was described by Sollas (1888, p. 272) from 

 Punta Arenas, Central America. There is a large port by this name 

 on the Pacific coast of Costa Rica, presumably the locaUty referred to. 

 It appears to be a form characteristic of this portion of the world. 

 There is no significant difference between the specimen found on the 

 Pacific side of Panama and those found at the Atlantic side. 



Genus GEODIA Lamarck 



GEODIA GIBBEROSA Lamarck 



This massive species is represented in the collection by U.S.N.M. 

 no. 22217, from the Pacific side, and no. 22231, from the Atlantic side 

 of Panama. It is gray-white, cartilaginous in consistency, and has a 

 surface hispid in places only. The pores are very conspicuous, about 

 1 mm apart and 0.3 mm in diameter. The oscules are equally con- 

 spicuous, circular, in depressed areas, and are about 1 to 3 mm in diam- 

 eter. There is a cortex 0.5 to 1 mm thick, which is densely packed 

 with spherasters about 60^ by 75/i The endosome is strongly radiate 

 with piincipally large oxeas, about 27^ by 800/x or larger, and plagio- 



