448 PROCEEDINGS OF THE NATIONAL MUSEUM vol.83 



exposed by the retreating tide only because of being at the center of 

 stellate figures made by radiating subdermal canals; othermse they 

 would be overlooked. They are closed (perhaps by sphinctrate 

 action) practically to zero diameter. In the endosome there are 

 plumose ascending tracts ending at the surface in brushes of spicules. 

 An approximate diameter of about 100^ might be assigned to them. 

 There is only one type of megasclere, a tylostyle varying from about 

 7m by 300/x to 10^ by 300ai. The microscieres include palmate aniso- 

 chelas of two size ranges, the larger about 22/x to 25ju, the smaller 

 about 12/i to 15m- In face view the alae of these anisochelas seem to 

 be extraordinarily narrow, only about one-fifth of the length of the 

 spicule. As a result of this, in special spicule preparations, they 

 usually lie on the side. Among them are fairly numerous sigmas 30m 

 in length of chord. 



c ^ ^ ^ 



FiGUEE 41. — Mycale cecilia, new species: Spicules, X 444 (camera lucida). a, Megasclere (tylostyle); 6, two 

 views of the sigmas; c, front view of the anisochela; d, side views of the chelas, showing extremes in size 

 (there are intermediates). 



The common West Indian Mycale, which is AI. angulosa (Duchas- 

 saing and Michelotti, 1864, p. 89) has peculiarly narrow anisochelas, 

 but its megascleres are exceedingly tliin, only 1m to 4m in diameter, in 

 contrast to 7m to 10m in the Panama sponge. Furthermore, A/, angu- 

 losa is a sponge that quickly grows up coarse and erect with hollow 

 cylindrical form predominating; it is cavernous and reddish brown. 

 Mycale imperfecta Baer (1905, p. 20) from the east coast of Africa 

 also has relatively narrow anisochelas, but these are of only one sort, 

 and its megascleres are small, only about 3m by 200m, whereas its sigmas 

 are large, frequently reaching nearly 80m in chord length, and 3m in 

 thickness. Probably the closest relative to cecilia is Mycale phyllo- 

 phila Hentschel (1911, p. 294). Its megascleres did not attain the 

 thickness of those in cecilia. It is represented only by tliin specmiens 

 growing on leaves. Were larger and maturer specimens available, 

 further points of difference from the Panamanian sponge might be 

 expected to appear. 



Genus MICROCIONA Bowerbank 



MICROCIONA ATROSANGUJNEA Bowerbank 



This species is represented in the collection by U.S.N.M. no. 22204. 

 It occurs rather commonly on the rocks in the intertidal zone at 

 Panama City as a bright-red, thin encrustation. Some of the smooth 



