THE SPONGES OF THE WEST-CENTRAL PACIFIC 29 



many of which are the exceedingly long meandrine canals leading to or 

 from the flagellate chambers. Others of the strands are probably symbiont 

 algae. 



The skeleton comprises principal fibers which are about 150 /x, in diameter 

 near the surface of the sponge, and become gradually larger until in the 

 deeper portions they reach a diameter of 500 /x. These are of clear yellow 

 spongin, pronouncedly laminate, and they usually (but not always) contain 

 a central core, which is filled with foreign debris. 



There are two other species in this genus : the type is Druinella rotunda 

 Lendenfeld, 1889, page 427, from Australia, and the other was first described 

 as Cacospongia camera by de Laubenfels, 1936, page 35, from the West 

 Indian region. The first of these was digitate, the second ramose. Each of 

 them was purple-red, with a reddish-gray interior, quite different from that 

 of tyroeis. The first had exceedingly lumpy fibers, and the genus Druinella 

 was first erected with a diagnosis based upon this lumpiness. Neither of the 

 other species has it. Camera had almost no debris in the fibers, but rotunda, 

 like tyroeis, had a great deal of foreign material. As de Laubenfels, 1948, 

 page 97, points out, the genus is most sharply characterized by the exceed- 

 ingly elongate, thin canals that lead to and from the flagellate chambers. 



The specific name tyroeis is derived from a Greek word for "cheese," 

 referring to the peculiar consistency of this species. 



GENUS THORECTOPSAMMA Burton 

 Thorectopsamma mela, new 



Text Figure No. IS 

 Plate VIII, Figure b 



This species is here represented by the following : 

 U.S.N.M. No. 22932, My No. M. 302, here designated as type, collected on 



June 11, 1949, by hand while wading at Ailing-lap-lap Atoll at the south 



portion of the lagoon near Bikajela Islet. The depth was just below low 



tide, and the substrate was dead coral. 

 U.S.N.M. No. 22938, My No. M. 308, collected on June 20, 1949, by diver 



in the deep entrance channel east of Bikajela Islet at Ailing-lap-lap 



Atoll. The depth was 10 meters, and the substrate was dead coral. 

 U.S.N.M. No. 22944, My No. M. 315, collected on June 21, 1949, by diver in 



the north portion of the lagoon near Matien Islet at Ailing-lap-lap Atoll. 



The depth was 5 meters, and the substrate was dead coral. 

 U.S.N.M. No. 22986, My No. M. 364, collected on July 5, 1949, by diver at 



Ebon Atoll in the south corner of the lagoon, in the miniature lagoon. 



The depth was 2 meters, and the substrate was dead coral. 

 U.S.N.M. No. 22989, My No. M. 367, with the same collection data as the 



preceding specimen. 

 U.S.N.M. No. 23007, My No. M. 387, collected July 11, 1949, by diver at 



