Plate 51 



Fig. 1. Costifer vasiformis. a, inicroxeas ; b, inicrostrongyles ; c, streptas- 

 ters. X150. 



2. Aciculites ciliata. Undeveloped desmas from just below dermal 



membrane of margin of the cup-shaped sponge, a, very young; b, 

 somewhat older; c, still older form. X220. 



3. Aciculites ciliata. Part of adult desma, showing characteristic tu- 



bercles. X220. 



4. Leiodermaimm pfeifferae (Carter). Part of a desma showing a 



rosette of three bidentate spinous tubercles, a single sharp biden- 

 tate tubercle, and a concave facet for zygosis. X400. 



5. Leiodermatium pfeifferae (Carter). Articulation of a simple kind. 



A clad, a. p., of one desma is simply apposed to another desma. 

 X220. 



6. Leiodermatium pfeifferae (Carter). An entire desma. X220. 



7. Leiodermatium pfeifferae (Carter). Part of desma bearing spinose 



tubercles embraced by an expanded articular process, a, p., of an- 

 other desma. X400. 



8. Brachiastcr simplex. Cladome of adult desma (a dichotriaene) ; 



most of the secondary branches with tertiaries, one with quarter- 

 nary branches, a. s., articular surface ; b. s., broken surface. 

 X85. 



9. Brachiaster simplex. Young desmas. a, simple dichotriaene form. 



6, simple dicho-mesotriaene form, c, mesotriaene in which two of 

 the primary clads and the distal axial ray break up, each into 

 three branches ; rhabdome unbranched ; nearly all secondary 

 branches beginning to acquire tertiary branches. XS5. 

 10. Phyllospongia aliena. Part of a section through the lamellate sponge, 

 vertical to the surface and radial to the free margin of the sponge ; 

 figure includes both surfaces, r. f., radial fiber ; s. c, sand cortex. 

 X20. 

 S1709— 25 17 521 



