310 Mr. H. J. Carter on the Stroraatoporidse. 



ultimate form of the sponge, whether branched or massive, is 

 attained ; but as this increase is only attended with a trans- 

 formation of the old surface into the internal structure, and 

 the groups of spongozoa go on increasing, while they do not 

 die out in the interior, the excretory canal goes on increasing 

 in size also, until of necessity (that is, from its importance) it 

 becomes the most prominent feature in the structure of the 

 sponge, agreeing in this matter with the excretory canals in 

 all animals, which are largest and most dilated at their outlet 

 — trumpet-shaped. 



Hence to have a sponge without a distinct excretory canal- 

 system which, from its preponderance over the other structures, 

 can be seen wkli the naked eye, would be an impossibility ; 

 while the nature of a coral-animal requires nothing of the 

 kind, since it is situated on the surface of the mass and 

 discharges the refuse of its food through the same orifice 

 by which it entered the body on the spot. 



Having now considered the structure of these recent animals, 

 let us turn our attention to that of tiie fossilized forms called 

 Stromatojyora. And here it is desirable to premise that they 

 will be treated of under the family name of Strom at oporidge, 

 in which the genera Btromatopora and Caunopora will be 

 included, and the latter described first, as it is partly through 

 Gaimopora that we shall have to ally Stromatopora to Mille- 

 pora alcicornis and thus to Hydractinia. 



In 1840 (Trans. Geol. Soc. Lond. vol. v. pt. 3) Lonsdale 

 figured and described Caunopora, Phill., under the provisional 

 name of Coscinopora placenta^ observing that " other speci- 

 mens [of Caimopora] might be mistaken for Btromatopora 

 concentricaj except that the tubes [the italics are mine] with 

 careful search may always be found." 



In 1841 Phillips ('Palseozoic Fossils of Cornwall, Devon, 

 and West Somerset ') gave the name of " Caunopora " to this 

 genus, again with reference to the " tubes ;" while Baily, 

 in 1876 (' Characteristic Brit. Fossils'), calls it Stromatopora 

 placenta^ Lonsdale, previously named by Rosen Stromatopora 

 Schmidtii (' Ueber die Natur der Stromatoporen und iiber die 

 Erhaltung der Hornfaser der Spongien im fossilen Zustande,' 

 Dorpat, lh67, Taf. 4, 5). Finally it has been illustrated by 

 Nicholson and Murie under the name of Caunopora (Linn. 

 Soc. Journ., Zool. vol. xiv. p. 219, and pi. ii. fig. 4). 



The necessity of making this a distinct genus of the 

 Strom atoporidai with a different name will hereafter appear 

 evident; and as the latter has already been done, I shall 

 allude to it under the name of Caunopora (Phill.) placenta^ 

 Lonsdale. 



