120 Canadian Record of Science. 



reached respecting the coal itself, and even some of the 

 plants associated with it. I therefore submitted to Mr. 

 Salter and published in my new edition the following facts, 

 tending to show that my so-called Naiadites were fresh- 

 water or estuarine shells. 



1. Undtr the microscope the thicker shells, even those of 

 the Anthracoptera type which most resemble marine species, 

 present an internal lamellar and subnacreous layer and a 

 thin layer of vertical prismatic fibres, covered with a well 

 developed epidermis in the manner of the shells of the 

 Unionidse or freshwater mussels. 



2. The ligament uniting the valves was external, and 

 there seem to have been no hinge teeth. The shells were 

 closed or very slightly open posteriorly, and in some species 

 there are indications of a byssus or ' : beard " for attach- 

 ment. The general aspect is in some species that of 

 mussels, in others that of Unios or Anodons. 



3. I know of no instance of the occurrence of these shells 

 *n the marine limestones or in association with species 

 known to be marine. 



4. The mode of their occurrence precludes the idea that 

 they were burrowers, and favors the supposition that they 

 may have been attached by a byssus to floating timber and 

 to one another. 



5. The attachment of shells of spirorbis to the outer sur- 

 face of many specimens seems to show that they were free 

 in clear water when living, while the dense piling together 

 of these shells in some beds almost unmixed with other 

 material, and their occasional occurrence in patches asso- 

 sociated with fossil wood, points to the same conclusion. 



6. They are associated with fine sediments, vegetable de- 

 bris, the crusts of minute crustaceans and remains of fishes 

 more likely to have been inhabitants of fresh or brackish 

 water than of the sea. 



On these grounds, and being unable from the specimens in 

 my possession to make out evidence of generic distinction, I 

 continued to use the name Naiadites ; using however, Salter's 

 names as subgeneric," so as to keep our species in harmony 

 with those of England as described by the Geological 



