AQUATIC ANIMALS OF Till: COAL. 



203 



■re allied to Unionidce, and that theii nearest analogue may be the 

 .mis Bysso-anodonta of [yOrbigny, found in the River Parana.* 



Mr Salter, h.-wever, to whom I sent specimens, regards these shells as 

 belonging to his new genera Artfhracomya and Anthracoptera, the 

 former being supposed to be allied to Myadat.\ More recently 

 Gttmbel and Geinitz have described similar shells from Thnringia as 

 belonging to the genera Unio and Amnion, and regard my Naladites 

 carbonarius (Anthracoptera carbonaria of Salter) as a l)reissena.\ 

 In the present uncertainty as to their genuine relations, I shall retain 

 the name Naiadites for the whole of the species, giving, however, 

 Salter's generic names in brackets. The genus Anthracosia of King, 

 which is evidently distinct from Naiadites, has been recognised in 

 Nova Scotia only in the Lower Coal formation of Baddeck, C. B. A 

 specimen found at that place by Mr Barnes will be noticed in the 

 sequel. As these shells swarmed in the waters of the Coal formation 

 estuaries or lagoons, facts tending to the elucidation of their habits 

 and affinities are important with reference to the coal ; I would there- 

 lure make the following remarks in relation to thein : — 



(1.) Under the microscope, the shells of the thicker species, as 

 Naiadites carbonarius, present an internal lamellar and subnacreous 

 layer, a thin layer of vertical prismatic shell, and an epidermis — these 

 structures being entirely similar to tbose of Unionidce. In the thinner 

 species, as in N. lavis, only the prismatic coat appears, and in this the 

 prisms are in some instances placed obliquely. These thin shells, 

 however, show evidence of an epidermis. (2.) The ligament was 

 external, there seem to have been no teeth, the shell was closed 

 posteriorly; but there arc indications of a byssal sinus. Mr Salter 

 describes the epidermis as wrinkled posteriorly; but this, with the 

 exception of the rings of growth, appears to me to result from pressure. 

 The shells are equivalve, and have the external aspect of Unionidce 

 or MytUidce. (3.) I know of no instance in Nova Scotia of the occur- 

 rence of these shells in the strictly marine limestones, nOr have any 

 properly marine forms of Mollusca been found with Naiadites in the 

 1 measures. (4.) The mode of their occurrence precludes the idea 

 that they were burrowers, but favours the belief that they were 

 attached by a byssus to sunken or floating timber. On the whole, I 

 think that the balance of probability is in favour of the conclusion 

 that they were brackish-water or fresh-water shells, allied to Mytilidas 

 or to embryonic Unionidce. 



* Supplement to Acadian Geology, 1860. 



f Quart. Journ. Geol. Soc, vol. xix. p. 79. 



j Neucs Jahrbaoh, 1864 Geological Magazine, May 1865. 



