PLATE VI. 

 " HALICHONDRIA CONDENSA, Bowerbanlk. 



Fig. 1. Represents the sponge based on a small 

 fragment of a bivalve shell. Natural size. 



Fig. 2. A small portion of the dermal membrane 

 exhibiting the unispiculous structure of its rete. 

 X 94 linear. 



Fig. 3. One of the short, stout, acerate spicula of 

 the skeleton. X 160 linear." 



" HALICHONDRIA CTLINDRACEA, Bowerlank. 



Fig. 4. Represents the sponge covering nearly the 

 whole of the carapace of a specimen of Jnachus 

 Dorsetensis, and appearing in small patches on some of 

 its leg-s. Natural size. 



O 



Fig. 5. One of the subcylindrical acerate spicula 

 of the dermal membrane. X 264 linear. 



Fig. 6. A bidentate, equi-anchorate, retentive spicu- 

 lum from the dermal membrane. X 425 linear. 



Fig. 7. One of the small, slender, bihamate, retentive 

 spicula from the dermal membrane. X 425 linear. 



Fig. 8. One of the subcylindrical, acerate skeleton 

 spicula. X 264 linear." 



