Plate 45. 



Fig. 1. Thenea grayi Sollas. Plesiasters. X220. 



2. Thenea grayi Sollas. a, b, metasters; c, spiraster. X220. 



3. Stelletta radicifera. a, dermal oxyasters ; b, ectosomal oxyaster with 



large centrum ; c, ectosomal oxyaster with smaller centrum and 

 fewer rays; d, ehoanosomal oxyaster with no centrum. X600. 



4. Sphinetrella bifacialis. Part of a vertical section including upper 



surface, w. s., lateral surface, /. «., and cloacal wall, c. ic, of sponge 

 The outer, o. m., and cloacal, e. m., margins of upper surface both 

 bear long spicules ; canals open on the cloacal surface. Somewhat 

 diagrammatic. X4. 



5. Erylus cor nut us. a, microrhabds ; b, strongylasters. X400. 



6. Sphinctrella bi facialis. Streptasters. X220. 



7. Characclla abbreriata. a, ehoanosomal microxea ; b, dermal microxea ; 



c, streptaster. a, b, X240; c, X600. 



8. Povciliastra ciliata. a, ehoanosomal microxea; b, dermal microxea; c, 



streptasters. a, b, X240; c, X600. 



9. Poecillastra ciliata. Skeletal arrangement of dermal surface. Cladomes 



of triaenes bound meshes ; in each mesh a canal aperture ; dermal 

 microxeas are represented in the enclosed mesh. X90. 



10. Characella abbrcviata. Skeletal arrangement; triaenes at the surface, 



and large projecting oxeas. From a section vertical to the surface. 

 X90. 



11. Stelletta radicifera. Cladomes of diehotriaenes at surface of sponge. 



X90. 



12. Tethyopsis dubia. a, b, c, d, strongylasters of four types; e, oxyaster. 



X 1,000. 



13. Stelletta radicifera. From a radial section: a, projecting protriaene ; 



b, anatriaene of radial bundle. X240. 



14. Tethyopsis dubia. Plagiotriaene. X90. 



15. Tethyopsis dubia. Orthodiaenes. a, type in which the long clad is 



dichotomous ; b, ordinary type. X45. 



16. Erylus cornutu*. From a vertical section through cortex of outer sur- 



face showing pore. p. in the sterraster-free area of dermal mem- 

 brane : incurrent ehone-canal, i. ch. c. : sphincter, sph, limiting the 

 aperture, ay, of chone canal into subcortical canal, s. c. X25. 



515 



