Ui7 



PLATE LXV. 



Ophlitaspongia seeiata, Bowerbanh. 



Vol. ii, p. 376, ' Mon. Brit. Spongiadas.' 

 Chalina seriata, Bowei'bank. 



A reconsideration of the structure of the skeleton 

 of this sponge has convinced me that its proper jilace 

 is in the genus Ophhtaspongia. The fibres of its 

 skeleton are exterspiculate, while those of every 

 species of British Chalina are interspiculate, an im- 

 portant anatomical difference that naturally assigns 

 them to different genera. 



Fig. 1. — Represents a fine specimen based on a piece 

 of rock, from one of the small caves of St. Katherine's 

 Rock, Tenby. Natural size. 



Fig. 2. — One of the subfusiformi, acuate, slender 

 tension spicula of the dermal membrane. X 250 

 linear. 



Fig. 3. — A slender, tricurvate, acerate tension sjoi- 

 culum from the dermal membrane. X 630 linear. 



Fig. 4. — One of the large, internal, defensive 

 spicula based on the skeleton-fibre of the sponge. X 

 250 Hnear. 



In vol. i, Plate XVII, fig. 287, a portion of a thin sec- 

 tion of the sponge at right angles to the surface, X 108 

 linear, illustrating the form of the Keratose skeleton, 

 and the mode of disposition of the internal defensive 

 spicula on its fibre. 



I have received from Mr. C. W. Peach a specimen of 

 this species from Fowey ; it surrounds the stem of a 

 Fucus for seven inches of its length, 



Spongionblla pulghella, Boiuerbank. 



Vol. ii, p. 359, ' Mon. Brit. Spongiadae.' 



Fig. 5. — Represents the type-specimen of the species 



