326 



THE CANADIAN NATURALIST. 



[Vol. vi. 



ON THE GENUS OBOLELLINA, 



By E. Billings, F.G.S. 



Fig. 1, Dragram of the interior of the ventral valve of a specimen, 

 supposed to he a small individual of 0. Canadensis ; bb, the two large 

 suh-centra] muscular impressions ; dd^ the groove under the area; e, 

 enlargement of the same ; ff, the pedicel groove in the area, on each 

 side of which is a smaller oblique furrow ; r, the ridge in front of the 

 muscular impressions. 



2. Interior of a dorsal valve ; a, the area ; c, the pair of small scars 

 in front of the two larger. The other letters, the same as in Fig. 1. 



3. Dorsal view of the original specimen. 



4. Side view of the same. 



5. Ventral view of the same. 



A short notice of this genus was published in the last number 

 of this journal, Dec., 1871. I now propose to extend the des- 

 cription, so far as our present material will admit. 



(All the figures in this paper are of the natural size.) 



