PLATE XLVl. 117 



minally incipiently spinous spicula, of the dermal 

 membrane. X 250 linear. 



Fig. 18. — One of tlT.e subfiisiformi-acuato skeleton 

 spicula. X 250 linear. 



Fig. 19. — A simple, biliamate, retentiye spiculum, 

 from the interstitial membranes. X 530 linear. 



HalichondkIxI Ingalli, Bou-ierfjunh. 



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



Fig. 20. — Represents tbe type-specimen in tlie dried 

 state. Natural size. 



Fig. 21. — A slender, subfusiforiu, cylindrical spi- 

 culum, from tlie dermal membra}ic. 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 

 sjjiculum, from the dermal membi'ane. X 530 linear. 



Halichondeia Batei, Bowerbcmk. 



Vol. ii, p. 261, ' Mon. Brit. Spongiadce.' 



Fig. 25. — Represents the type-specimen as described 

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

 sponge H. Batei, and (5) 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 woidd 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 lai^ge, bidentate, equi-anchorate, reten- 



