HISTORICAL INTRODUCTION. 15 



and that the extinct genus Parheria, described by Dr. W. B. Carpenter as a Fora- 

 minifer, is also truly Hydrozoal and related to Hydr actinia. This memoir is the 

 first of a long and important series of papers in which Mr. Carter deals with the 

 recent HydractinicB and their extinct allies, and the result of which has been the 

 gradual conversion of palaeontologists to the view that the Stromatoporoids are 

 properly referable to the Hydrozoa. Leaving Parheria out of the question, as not 

 concerning us here, Mr. Carter in the memoir alluded to describes various recent 

 and fossil species of Hydractlnia, and gives an excellent account of the structure, 

 and also of the development, of the skeleton of Hi/dradinia echinata, Flem. He 

 maintains the opinion that the Stromatoporoids are extinct allies of Hydractinia, 

 and that they have nothing in common with the Sponges, to which they have been 

 referred by so many previous writers. The stellate canals (" astrorhiza? ") which 

 constitute such a conspicuous feature in many Stromatoporoids, and which super- 

 ficially exhibit such a sponge-like appearance, are parallelled by Mr. Carter with 

 the shallow, radiating, coenosarcal grooves which furrow the surface of the crust in 

 the recent HydractinicB. 



In a supplementary note to the English translation (' Ann. and Mag. Nat. 

 Hist.,' ser. 4, vol. xix, 1877) of his masterly memoir, entitled " Beitriige zur Sys- 

 tematik der fossilen Spongien " (' Neues Jahrbuch fur Mineralogie,' &c, 1877), 

 Professor Zittel gives his adhesion to Mr. Carter's view that the Stromatoporoids 

 are really to be regarded as allies of Hydractinia, and as belonging therefore to 

 the Hydrozoa. 



In an interesting and valuable memoir published in 1878 (' Palaeontographica,' 

 3 Folge, Bd. i, 3 Lief., p. 101), Dr. Steinmann also expresses the opinion that the 

 Stromatoporoids should be placed in the neighbourhood of the Hydract'miidai. 

 The author founds the genus Sphceractinia for certain concentrically-laminated 

 fossils from the Upper-Jurassic Rocks, which in internal structure present con- 

 siderable resemblance to certain of the Stromatoporoids. The genus Labechia, 

 B. and H., is regarded as constituting a connecting link between the Tabulate 

 Corals and the Hydractiniidce. The author also deals with Parheria, Carp., 

 Loftusia, Brady, and the three new genera Porosphcera, CyUndrohyphasma, and 

 MHpsactinia, all of which he considers as being related to the Hydractiniidce, and 

 as having, therefore, more or less close relationships with the Stromatoporoids. 



In the same year Mr. Carter published a second paper, " On New Species of 

 Hydractiniidae, recent and fossil, and on the Identity in Structure of Millepora 

 alcicomis and Stromatopora " ('Ann. and Mag. Nat. Hist./ ser. 5, vol. i, pp. 

 298 — 311). In this memoir the author compares the Stromatoporoids with 

 Millepora, and comes to the conclusion that there exists betweon them a sub- 

 stantial agreement in structure. The stellate canal-systems (" astrorhizaa ") of 

 many Stromatoporoids are compared with the irregular coenosarcal canals which 



