466 On Sponges from South Australia. 



together with their subdermal cavities and the general cavity 

 of that part of the sponge which is provided with this inhalant 

 structure. 



Again, with reference to the sponges which afford typical 

 illustrations of the structure of two of my orders in one, 

 nothing can be more decisive than that of Pseudoceratina 

 typica (p. 287), Pseudohalichondria clavilohata (p. 454), and 

 Pseudoesperia emgmatica (p. 455) respectively ; since wherever 

 they may be relegated hereafter, the fact of such opposite 

 structures existing together as parts of the same sponge is 

 established. 



The type specimens of those species which I have described 

 have, in accordance with Mr. Wilson's request, been deposited 

 in the British Museum. It may be added that they were 

 dredged in the month of January, and are mostly charged with 

 ova. 



EXPLANATION OF PLATE X. 



Fig. 1. PhlaocUctyo7i birotuliferum, nat. size. «, main trunk ; 6, branches; 

 c, bud ; d, portion of internal layer hanging out of the main 

 trunk ; e, smooth portion ; /, poriferous portion, represented by 

 the puncta. 



Fiff. 2. The same. Skeletal spicules and flesh-spicule relatively magni- 

 lied to the scale of l-12th to l-1800th inch, a, large skeletal 

 spicule ; b, smaller one ; c, flesh-spicule. 



Fig. 3. The same. Flesh-spicule more magnitied. a, lateral view ; b, 

 end view. Scale 1 -12th to l-6000th inch. 



Fiff, 4. The same. Surface of internal layer of poriferous portion of 

 branches, magnified to the scale of l-tSth to 1-lSOOth inch. 

 Diagrammatic, showing : — a, internal, clathrous, sarco-fibrous 

 layer ; bbbb, infundibular depressions of the same ; cc c c, exter- 

 nal apertures of infundibular depressions ; ddd cl, pore-structm'e 

 of the surface as seen through the infundibular depressions when 

 the object is placed between the eye and the light. 



Fig. 5. The same. Surface of external layer of poriferous portion of 

 branch, magnified to the scale of l-48th to 1-lSUOth inch. 

 Diagrammatic, showing : — a a a a, middle layer or large skeletal 

 structure ; bbbb, external laj'er, including epithelium and pore- 

 structure ; c c, spicular framework of this layer ; d, pores ; e ee, 

 circles representing external apertures of " infundibular depres- 

 sions " of inner layer, which can only be seen when the object 

 is placed between the eye and the light. 



Fig. G. rseitdohalichondria davilobata, half nat. size, a a a, lobes ; bbbb, 

 monticular elevations on the surface -,000, vents. 



Fig. 7. The same. Spieulation relatively magnified to the scale of l-24th 

 to l-GOOOth inch, a, skeletal spicule ; b, flesh-spicule, lateral 

 and front views. 



Fig. 8. The same. Flesh-spicule more magnified, o, lateral view ; d, 

 front view. 



Fig. 9. The same. External surface relatively magnified to the scale of 

 l-9Gth to 1-1 800th inch, a a, sarco-fibro-reticulate structure of 

 surface generally ; b b, pore-areas occupying the interstices of the 

 same, in which the pores are represented by the little circles ; 

 c, monticular elevation of surface ; d, projection of the sand-fibre, 



