Wright — List of Irish Cretaceous Microzoa. 89 



127. Furcated porrecto-ternate moniliform spiculum, PI. II. fig. 5. This is 

 probably an external defensive spiculum from a Sponge closely allied to 

 Tethea. I have seen from our southern Chalk the same form with monili- 

 form shaft and radii, but not so distinctly banded. Rather rare. 



128. Equiangular triradiate spiculum, PI. II. fig. 6, This form occurs as a 

 siliceous form rarely, but abundantly in the calcareous Sponges as skeleton 

 spicula. Rare. 



129. Spiculated equiangular triradiate spiculum, PI. II. fig. 7. This occurs 

 as a siliceous form rarely, but abundantly in the calcareous Sponges as 

 internal defensive spicula. * Abundant. 



CONNECTLNG-SPICULA. 



130. Incipiently expanso-ternate spiculum, probably from a Geodia, PI. II. 

 fig. 8. It is not uncommon in our southern flints. Rare. 



131. Expando-ternate spiculum ; closely allied to the last, PI. II. figs. 9 and 10. 

 This form is found in recent Tethea, Geodia, and other genera. Frequent. 



132. Expando-ternate spiculum, with cylindrical radii, PI. II. figs. 11 and 12. 

 This form is found in some recent species of Tethea, but is not a normal 

 condition. Rather rare. 



133. Furcated attenuato-patento-ternate spiculum, PI. II. fig. 13. This con- 

 stricted form of an apparently furcated attenuato-patento-ternate spiculum 

 has not yet been found among recent Sponges. It occurs in our southern 

 Chalk flints. Rather ^rare. 



134. Furcated attenuato-patento-ternate spiculum, PI. II. figs. 14 to 16. This 

 form of spiculum abounds in the expansile dermal system of several of the 

 siliceo- fibrous Sponges, as in that of Dactylocalyx Bcnverbankii, Johnson 

 (Proc. Zool. Soc. 1869, PI. III. figs. 6, 7). These spicula vary in form 

 and size to a considerable extent in the same species. In great profusion. 



135. Furcated attenuato-patento-ternate spiculum, PL II. fig. 17 ; from the 

 expansile dermal system of a siliceo-fibrous Sponge. In great profusion. 



* This rarity of some of our forms of spicula in recent siliceous Sponges is of con- 

 siderable interest, in connection with the fact that all the little organisms in the powder 

 from our flints seem to be now silicified, whether they were originally calcareous (as the 

 Foraminifera and Ostracoda) or not. 



