SILICIOUS AND HORNY SPONGES WILSON. 453 



subdivided. Or the unexpanded end of the lobelike clad may be 

 subdivided by a shallow notch into two secondary lobes. Greatest 

 diameter of cladome 180-450 [x. 



Long slender smooth rhabds occur in the ectosome of the dermal 

 and gastral surfaces. In the dermal ectosome they form radial 

 bundles, and are also scattered singly. In the gastral ectosome they 

 form both radial and tangential bundles. The spicules, which are 

 difficult to isolate whole, reach a length of 420 pu and are 4-6 \l thick. 

 They include strongyles with slightly tylote ends and styles which 

 taper evenly to a point and are placed with the rounded end outer- 

 most. 



Microrhabds form a crust at the dermal and gastral surfaces, and 

 are abundant in the interior. They measure 8-12 [i. in length, 2 [i. 

 thick; surface prickly; ends strongylate or oxeate. 



Holotype.— Cut. No. 21304, U.S.N.M. 



From the fact that in this sponge the cloacal membrane includes 

 phyllotriaenes, it is probable that the cloaca is to be looked on as 

 having a different morphological value — that is, as having arisen 

 phylogenetically in a different way, and probably as produced 

 ontogenetically in a different way, from the cloaca of other species 

 of T heonella, such as T. swinhoei. In the latter species the lining 

 membrane of the cloaca (or cloacae) is like that of the canals in 

 general — namely, contains abundant microrhabds but no phyllo- 

 triaenes. The cloaca then in such species is probably to be looked 

 on as merely an enlarged canal, or as a space produced by the fusion 

 of canals during ontogenetic growth. In T . invaginata, on the con- 

 trary, the cloacal lining seems to represent an inturned part of the 

 ectosome — that is, a part which has become virtually inturned 

 through the continued upward growth of the margin of the young 

 sponge. 



Analogies to the species here described are presented by T. disci f era 

 Lendenfeld (1906, p. 351) from the west coast of Australia, and in a 

 less degree by T. lacerata Lendenfeld (1906, p. 347) from near 

 Sumatra. In the dermal phyllotriaenes of the latter species the 

 clads are very wide and irregular, sometimes undivided, the cladome 

 thus varying in the direction of the discotriaene (1906, pi. 44, figs. 

 1, 3). In the former species the dermal triaenes are a mixture of 

 phyllotriaenes, discotriaenes, and intermediate forms (1906, pi. 43, 

 figs. 8-12). The variation in these species toward the discotriaene 

 form, it will be noticed, affects the triaenes of the surface in general, 

 whereas in the Albatross species this tendency comes into activity 

 only over the inner (probably in an earlier stage of growth, the 

 upper) face of the sponge. 



