343 



PLATE XCII. 



ISODIOTYA TUMULOSA, Bowerbank. 



Fig. 1. Represents the type-specimen. ISTatural 

 size. 



Fig. 2. A skeleton spiculum. X 320 linear. This 

 figure also represents the acuate entirely spined tension 

 spicula of the porous areas. 



Fig. 3. One of the simple bihamate retentive 

 spicula of the dermal membrane. X 530 linear. 



Fig. 4. A contort bihamate retentive spiculum 

 from the dermal membrane. X 530 linear. 



Fig. 5. One of the very minute simple bihamate 

 retentive spicula. X 530 linear. 



Fig. 6. A bidentate equi-anchorate retentive 

 spiculum of the larger size. X 530 linear. 



Fig. 7. A spineless acerate spiculum with semi- 

 hastate termination from the skeleton structure. X 

 320 linear. 



BATTEESBYIA BUOKLANDI, Boiverlanlc. 



Hymeniacidon BucUandi. Vol. ii, p. 227, Mon. Brit. 



Spongiadae. 



Fig. 8. Represents a section of the type-specimen 

 at right angles to the external surface, exhibiting the 

 mode of disposition of the skeleton spicula. X 60 

 linear. 



HYMENIACIDON ALDOUSII, BowerdanJc t 



Fig. 9. Represents the type-specimen of the species. 

 Natural size. 



Fig. 10. An acuate skeleton spiculum. X 250 

 linear. This figure also represents the spicula of the 

 dermal membrane. 



Fig. 11. A very slender form of the skeleton 



