181 



PLATE LXXI. 



Hymeniacidon I'OLIATUS, Bo'iverhavk. 



Fig. 1. — Re^Dresents a portion of the skeleton of tlie 

 type-specimen, exhibiting the mode of the arrangement 

 of the skeleton structure. X 123 linear. 



Fig. 2. — A fully-developed spinulate skeleton spi- 

 cuknn. X 250 linear. 



Desmacidon conSteiotus, BoioerbanJc. 



Vol. ii, p. 350, ' Mon. Brit. Spongiadfe.' 



Fig. 3. — Represents a portion of the skeleton struc- 

 ture of the type-specimen of the species, exhibiting the 

 large size of its multi-spiculous skeleton fibres, and a 

 portion of the interstitial membrane and its dispersed 

 tension spicula. X 36 linear. 



Fig. 4. — One of the subfusiformi-acuate skeleton 

 spicula, exhibiting its basal constriction. X 250 

 linear. 



Fig. 5. — The basal portion of another skeleton 

 spiculum showing a still greater amount of constric- 

 tion. X 250 linear. 



Fig. 6.— Another basal portion of a skeleton spi- 

 culum with a hastate basal termination. X 530 

 linear. This form of the base prevails in a more or 

 less degree in a considerable number of the skeleton 

 spicula. 



Fig. 7. — A small dentato-palmate inequi-anchorate 

 spiculum. X 530 linear. 



Fig. 8. — One of the large dentato-palmate inequi- 

 anchorate spiculum. X 530 linear. 



Fig. 9. — A large bidentate inequi-anchorate spicu- 

 lum. X 530 linear. This form often occurs along 

 with the dentato-palmate ones. 



Fig. 10. — Two of the contort, bihamate, retentive 

 spicula. X 530 linear. 



