357 



belong to one generic group closely related to Calatldum. This latter 

 passes into Eospongia, which, in its turn, gradually merges into other 

 genera that occur in more recent formations, such as Rhysospongia, 

 Scyphia, Siphonia, and others. The resemblance between the whole 

 structure and that of the palsezoic corals seems also to shew that in the 

 Lower Silurian seas organic forms existed combining the characters of the 

 Protozoa and the Coelenterata. 



GENUS TRICHOSPONGIA. (N. gen.) 



G-eneric Characters. This genus occurs in rudely hemispheric masses 

 from one to five inches across. The skeleton appears to be minutely 

 fibrous, and is full of elongate cylindrical or acerate spicula just visible to 

 the naked eye. In silicified specimens that have been treated with acid 

 there are seen numerous irregular branching canals from one to six lines 

 in diameter. 



TRICHOSPONGIA SERICEA. (N. sp.) 



Description. The form appears to be rudely hemispherical, and from 

 one to five inches in diameter. In one specimen an imperfect concentric 

 structure is obscurely indicated. In a very small individual there is a 

 deep concavity in one side, which may be the cup. 



The specimens are very imperfect, consisting, in general, of portions 

 which were sufficiently silicified to resist the acid, and very little can be 

 determined with certainty as to the form. All the fragments that have 

 been observed appear to belong to one species. 



Locality and Formation. Mingan Islands ; Calciferous formation. 



Collectors.' Sir W. E. Logan and J. Richardson. 



GENUS RHABDARIA. (N. gen.) 



Generic Characters. This genus is proposed for the reception of 

 certain small cylindrical bodies which were found in the residue left after 

 dissolving pieces of the magnesian limestone from the Mingan Islands in 

 acid. They are from one to four lines in diameter, with a rough surface, 

 and have a small perforation along the centre. There are two species 

 which I propose to name provisionally as follows : 



1. Rhabdariafragilis. Small cylindrical stems, with a rough exterior, 

 and a central perforation or canal. At first these were thought to be 

 silicified specimens of Stenopora fibrosa, but when others were procured 

 shewing the central canal, it became evident that they could not be thus 



