126 



Canadian Record of Science. 



Epidermis thick and sometimes wrinkled, especially in 

 flattened specimens, shell substance usually very thin. 



Shells of this genus are more widely distributed, both 

 locally and in time, in the coal-formation of Nova Scotia, 

 than those of the previous genus. Shale surfaces are some- 

 times crowded with them, though they do not so much 

 enter into the composition of beds of some thickness. 

 There are several species, varying a good deal in form, 

 some being nearly circular, while others are much elongated. 

 There are also two types, one more attenuated and gibbous 

 in front and therefore assuming a more mytiloid aspect, 

 {e.g. A. elongata), the other more regularly oval and Unio- 

 like in form (e.g. A. arenacea). The first type is in some 

 degree a passage, so far as form is concerned, to the genus 

 Naiadites. The internal surface is not known. 



It is noteworthy that while several of the species range 

 from the Lower Carboniferous or the millstone grit to the 

 upper coal measures, the individuals are usually smaller 

 and more depauperated in the lower beds. 



1. Anthracomya elongata, Dawson. 



Figs. 6, 7, 8. — Anthracomya elongata, Middle Coal-formation, 

 S. Joggins and Mabou, C. Breton. Fig. 6.— Small specimen .natural 

 size and enlarged. Fig. 7.— Large specimen, natural size. Fig. 8.— 

 Medium specimen with spirorbis attached and anterior end slightly 

 crushed in. Enlarged x 1^. 



