PLATE XLV1. 



miimlly incipiently spinous spicula, of the dermal 

 membrane. X 250 linear. 



Yig. 18. One of the subfusiformi-acuate skeleton 

 spicula. X 250 linear. 



Fig. 19. A simple, bihamate, retentive spiculum, 

 from the interstitial membranes. X 530 linear. 



HALICHONDRIA INGALLI, Bowerbank. 



Vol. ii, p. 258, ' Mon. Brit. Spongiadae.' 



Fig. 20. Represents the type-specimen in the dried 

 state. Natural size. 



Fig. 21. A slender, subfusiform, cylindrical spi- 

 culum, from the dermal membrane. X 250 linear. 



Fig. 22. One of the attenuato-acuate, basally- 

 spined, skeleton spicula. X 250 linear. 



Fig, 23. One of the malformed, bihamate, retentive 

 spicula, from the dermal membrane. X 530 linear. 



Fig. 24. An angulated, inequi-anchorate, retentive 

 spiculum, from the dermal membrane. X 530 linear. 



HALICHONDRIA BATEI, Bower bank. 



Vol. ii, p. 261, ' Mon. Brit. Spongiada?.' 



Fig. 25. Represents the type-specimen as described 

 in p. 261, vol. ii. Of the natural size ; (a) is the 

 sponge H. Batei, and (b) a portion of a young specimen 

 of Dictyocylindrus rugosus rising above it. The 

 whole of the cup of Isodictya infundibuliformis has 

 not been figured, as it would have occupied too great 

 an amount of space in the Plate. 



Fig. 26. One of the obtusely pointed, acuate, ten- 

 sion spicula, of the dermal membrane. X 250 linear. 



Fig. 27. One of the stout, acuate, entirely spined, 

 skeleton spicula. X 250 linear. 



Fig. 28. A large, bidentate, equi-anchorate, -reten- 



