SILICIOUS AND HOB NY SPONGES WILSON. 295 



overlapping so as to enclose polygonal areas; other cladomes deeper 

 in the ectosome. Rhabdome 3.4-5 mm. by 44 [x; protoclad 80 [x long; 

 deuteroelads 100-190 jx long. The intermingled smaller spicules 

 with very short deuteroelads are doubtless young forms, and indi- 

 cate that the protoclad reaches its full length although not its 

 thickness while the deuteroelads are very small. 



Among the projecting spicules of lower half of body are some 

 dichotriaenes. 



(2) Anatriaenes (pi. 45, fig. 13). Present but not abundant in the 

 radial bundles. Cladomes in ectosome and peripheral choanosome. 

 Cladome rather shallow, apex rather sharp. Rhabdome may be as 

 long as 8 mm.; 10 [x thick. Clads 40-60 [x long. Similar anatri- 

 aenes occur among the projecting spicules of the lower bod}', prob- 

 ably abundantly, but the ends are more often broken off. The clads 

 are sometimes reduced, spicule becoming an anamonaene; clad up 

 to 70 [x long, rhabdome 8-16 jx thick. 



(3) Protriaenes (pi. 45, fig. 13). A few present in the radial 

 bundles, cladome in the ectosome. Rhabdome long, 8 jx thick; clads 

 60-100 [x long. Similar protriaenes, with rhabdome 4.5 mm. by 8 jjl, 

 and clads 20-60 [x long are abundant among the projecting spicules 

 of the lower body. Stronger protriaenes also occur among these 

 projecting spicules; rhabdome 40 fx thick at the thickest point, taper- 

 ing somewhat toward outer as well as toward inner end: clads 

 strong, 50-85 [x long, sometimes rounded at the apex instead of 

 pointed, sometimes unequal in length. 



(4) Oxea. Abundant in the radial bundles ; 3.4-4.5 mm. by 35-50 [x. 

 Also among the projecting spicules of the lower body, where the 

 thickness may reach, 70 ;x. 



(5) Dermal oxy aster (pi. 45, fig. 3, a). Abundant, forming a 

 crust. With small centrum and relatively long tapering rays. Total 

 diameter, 8 [x. 



(6) Oxyasters of interior, (a) Ectosomal oxyasters (pi. 45, fig. 3, 

 b, c) abundant, 8-20 [x diameter, varying from a type without obvious 

 centrum and 6-7 rays to a type with conspicuous centrum and more 

 numerous rays. The centrum is most conspicuous and the rays 

 most numerous in the largest spicules, but these are scanty. The 

 spicules commonly range 12-16 [x in diameter, have a perceptible 

 centrum and a number of rays greater than in the choanosomal type. 

 (b) Choanosomal oxyasters (pi. 45, fig. 3, d) scantily present. About 

 16 [x diameter, with a few (6-7) long slender rays; without centrum. 

 The asters of all the types intergrade. 



B'olotype — Cat. No. 21301, U.S.N.M. 



The Albatross species, as will have been seen, has the following 

 complex of megascleres: Oxeas, dichotriaenes, anatriaenes, protri- 

 aenes. The only recorded species of the genus, sens, sir., having the 



