194 PROF. H. A. NICHOLSON AND DB. J. MUBIE ON THE 



nifer, is also truly Hydrozoal and related to Hydractinia. Upon 

 this point we must speak with considerable diffidence, as not 

 having seen and examined the specimens upon which Mr. Car- 

 ter's views are based. "We have, however, examined a large 

 series of specimens and sections of Parkeria, including typi- 

 cal examples kindly furnished us by Dr. Carpenter himself; 

 and we believe the view that it is an Arenaceous Foraminifer to 

 be the one most in accordance with the facts exhibited by these 

 specimens. We quite admit the likeness in structure presented 

 by some forms of Stromatopora to Parheria ; but having arrived 

 at the conclusion that all the Stromatoporoids were primitively 

 calcareous, we are unable to admit that there is any real affinity 

 between these two groups of organisms. As regards the ordinary 

 forms of Hydractinia, we can fully recognize the resemblance 

 which these present to the Silurian fossils described by Milne- 

 Edwards and Haime under the name of Labechia, a resemblance 

 which, as we have already indicated, was long ago pointed out by 

 Lindstrom, though even in this case the apparently solid pillars 

 of Lahechia can hardly be paralleled with any structure present 

 in Sydractinia. We are not, however, so far as the extensive 

 series of specimens which we have examined will allow us to judge, 

 prepared to admit that any relationship of real affinity subsists 

 between Stromatopora and Hydractinia, though the existence of 

 calcareous species of the latter genus is certainly a noteworthy 

 fact. As to the existence, lastly, of siliceous species of Hydrac- 

 tinia, such as described by Mr. Carter from the Upper Greensand 

 of Haldon Hill, we think that it would be desirable to obtain 

 more evidence than has yet been published, proving that such 

 apparently siliceous forms are not merely silicified examples of 

 originally calcareous specimens. We do not of course assert that 

 this is the case ; but we think that this is a consideration which 

 cannot be overlooked in any discussion of this question. 



Lastly, Professor Zittel, in a supplementary note to the English 

 translation (Ann. & Mag. Nat. Hist. ser. 4, vol. xix. 1877) of his 

 masterly memoir entitled " Beitrage zur Systematik der fossilen 

 Spongien" (' Neues Jahrbuch fiir Mineralogie,' &c. 1877), 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*. 



* Since the above was written, the following additional papers upon the Stro- 

 matoporoids have been published or read : — 



