The Nautilus 
VOL. VIII. 
JULY, 1894. 
No. 3 
SYNOPSIS OF THE MACTRIDJE OF NORTH AMERICA. 
BY WM. H. BALL. 
In revising the group of Mactracea with the intention of working 
up the Tertiary species of North America it became necessary to go 
over the whole of the recent species and enquire into their synony¬ 
my. The following lists of east and west American species seem 
likely to be useful to students, as the synonymy of the group has 
been in a confused state hitherto. The distinctions between the 
different types of Mactriclce have hitherto largely been lost sight of, 
owing to the practice of confounding all together under one or two 
generic names ; and while, to those habituated to previous methods, 
the present arrangement may at first sight seem excessively sub¬ 
divided, I have found, in going over the whole group of Mactracea 
in the National Collection, that features of geographical distribution 
and characters of importance in the development of the family in 
time, are brought out by it in a way which was wholly impossible by 
earlier methods. The present subdivision compared with that of 
most other groups of mollusks at the present time is not excessive, 
and by those who may be led to a close and accurate study of the 
mollusks in question hereafter I believe it will be found to be useful 
and convenient. 
I. Synopsis of the Mactridpe of the Eastern coast of the United 
States. 
