24 DR. J. S. BOWERBANK ON THE SPONGIADJE. [Jan. 7, 



Fig. 3. An atteuuato-patenti-temate connecting spiculum of about the average 



size, magnified 80 linear. 

 Fig. 4. The head of one of the largest and most fully developed connecting 



spicula, magnified SO linear. 

 Fig. 5. One of the attenuato-stellate retentive spicula from the interstitial 



membranes, magnified 530 linear. 



Tethca simillima, Bowerbank. 



Fig. G represents the type specimen in spirit in the Museum of the Boyal College 

 of Surgeons, London : natural size. 



Fig. 7. The small specimen in the dried state, exhibiting a vievr of the external 

 surface, natural size. 



Fig. 8. A sectional view of the same specimen that is represented by figure 7, 

 showing the central nucleus and the mode of disposition of the skeleton- 

 fasciculi : natural size. 



Fig. 9. Two thirds of one of the large fusiformi-acerate skeleton-spicula, mag- 

 nified 80 linear. This figure also represents the same form of spiculum 

 as an external defensive one. 



Fig. 10. One of the fusiformi-porrecto-ternate external defensive spicula, mag- 

 nified 80 linear. 



Fig. 11. An attenuato-recurvo-ternate defensive spicu'um, with long and very 

 slender shaft, magnified 80 linear. 



Fig. 12. One of the stout fusiforini-aeerate spicula that surround the defensive 

 fasciculi of the external surface, magnified 80 linear. 



Fig. 13. A small portion of the skeleton of one of the gemmules of the sponge, 

 extending from its centre to its external surface, shewing its unihamate 

 and porrecto-ternate spicula in sihi, from a specimen mounted in 

 Canada balsam : magnified 80 linear. 



Tcthea Cliftoni, Bowerbank. 



Fig. 14. The type specimen, showing the remarkable mode of its location under 

 difficulties : natural size. 



Fig. 15. One of the fusiformi-acuate skeleton-spicula, magnified 150 linear. 



Fig. 16. One of the large sphero-stcllate spicula of the dermal rind of the sponge, 

 magnified 530 linear. 



Fig. 17. A minute subsphero-stellate retentive spiculum with clavated cylindri- 

 cal radii, magnified 530 linear. 



Fig. 18. A smaller specimen of the same description as that represented by fig. 

 17, magnified 530 linear. 



Plate IV. 



Lcuconia glomcrosa, Bowerbank. 



Fig. 1. The type specimen, natural size. 



Fig. 2. One of the equiangular triradiate spievda of the dermal membrane, mag- 

 nified 80 linear. 



Fig. 3. One of the largest-sized fusiformi-acerate dermal spicula, which has been 

 fractured near its middle and cemented together again : magnified 80 

 linear. 



Fig. 4. A small-sized fusiformi-acerate dermal spiculum, magnified 80 linear. 



Figs. 5 & 6. Two of the triradiate spicula of the interstitial skeleton, magnified 

 80 linear. 



Desmaeidon fistulosa, Bowerbank. 

 Fig. 7 represents the type specimen, natural size. 

 Fig. 8. One of the skeleton-spicula, magnified 150 linear. 



Ciocalypiu Ti/leri, Bowerbank, 

 Fig. 9. The type specimen, natural size, 



