122 Canadian Record of Science. 



family My til idae or mussels, the second as allied to Anodons 

 in the family of the Unioniche or freshwater mussels, as 

 they are sometimes called. 



Mr. Wheelton Hind gives the characters of the genera in 

 full. For these characters reference may be made to his 

 paper 1 ; but for the benefit of collectors, the following sum- 

 mary of the more important external points may be in- 

 serted here. 



Genus, naiadites, Dawson. 

 (Anthracoptera, Salter.) 



Shell Modiola-like, somewhat triangular in form, broad 

 and rounded behind, somewhat pointed in front, beak at 

 anterior extremity, almost terminal, and extending obliquely 

 backward in a more or less pronounced ridge, hinge-line 

 straight, sometimes showing delicate internal striae, teeth 

 rudimentary ; epidermis somewhat wrinkled, surface with 

 concentric lamellae and lines of growth. A few specimens 

 showing the interior indicate that the hinge-plate was finely 

 striated, and that there was a trifid anterior muscular scar 

 and a larger single posterior one. 



1. Naiadites carbonarius, Dawson. 



Figures 1 to 3. — Naiadites carbonarius, Middle Coal-formation, 

 S. Joggins. 1 and 2. — Original figures from imperfect specimens, 

 3. — More perfect specimen, enlarged x 2. 



1 Journal of Geological Society, May, 1893. 



