PLATE XV. 



TETHEA COLLINGSII, Bowerbank. 



Vol. ii, p. 87, ' Mon. Brit. Spongiadae.' 



Fig. 1. Represents the specimen found by me in 

 the second of the Guliot caves at Sark, in the condi- 

 tion in which it came from off the rock between high 

 and low-water marks. Natural size. 



There are the basal portions of several small Balani 

 firmly attached to its surface, indicating that it was 

 probably several years old. 



Fig. 2. - - A fusiformi-acerate skeleton spiculum. 

 X 80 linear. 



Figs. 3, 4. Minute, acerate, tension spicula of the 

 dermis. X 80 linear. 



Fig. 5. A large, attenuate-stellate, retentive - spicu- 

 lum from the dermal membrane. X 320 linear. 



Fig. 6. One of the small, attenuate-stellate, reten- 

 tive spicula of the dermal membrane. X 320 linear. 



Fig. 7. A fully -developed, geniculated, recurvo- 

 patento, ternate, connecting spiculum. X 80 linear. 



Fig. 8. The head of one of the geniculated, recurvo- 

 patento, ternate, connecting spicula, not completely 

 developed. X 80 linear. 



Fig. 9. One of the geniculated, recurvo-patento, 

 ternate, connecting spicula, in an early stage of deve- 

 lopment. X 80 linear. 



The immature spicula represented by figs. 8 and 9 

 are very numerous, and every possible intermediate 

 form between figs. 7 and 9 may be observed. 



In vol. i, plate ii, fig. 48, ' Mon. Brit. Spongiadse,' 

 there is a figure of one of the fully developed con- 

 necting spicula of this species as the type of a " genicu- 

 lated, expando-ternate," connecting spiculum. This 



