MOLLUSCA. 
I 26 
abundant in the mountains occur rarely, or not at all, in the latter 
section, and the converse is also, in a measure, true. Indeed, several 
genera, or subgenera, of each region are unrepresented in the other. 
Twenty-one species of land, and two of fresh-water mollusks which 
were collected, are named as follows by Mr. Henry Prime of River- 
dale : 
Macrocyclis concava Say, 
Zonites fuliginosus Griff., 
“ ligerus Say, 
“ inornatus Say, 
“ arbor eus Say, 
“ indentatus Say, 
“ minusculus Binn. (?),* 
“ Binneyanus Morse, 
“ exiguus Stimpson, 
“ fulvus Drap., 
“ multidenlatus Binn., 
Patula alternata Say, 
P. striatella Anth., 
Tebennophorus Carolinensis Bose., 
Hclicodiscus lineatus Say, 
Pallifera dorsalis Binn., 
Stenotrenia monodon Rack., and 
var. fraterna , 
Mesodon albolabris Say, 
“ dentifera Binn., 
“ Sayii Binn., 
Succinea obliqua Say, 
Physa heterostropha Say, 
Anodon Benedictii Lea. 
This collection was made without systematic or extended search, 
and, though it is to be considered as reasonably representative of the 
immediate localities explored, must necessarily be too imperfect for a 
broader application. 
Although justice cannot here be done to the Flora of the region it 
should not be passed over without some allusion to its decidedly 
Canadian characteristics. These, and the abrupt physiographical 
changes from contiguous regions which they represent, cannot be 
more clearly brought out than by comparison, and to this end the 
Flora of the vicinity of my own home at Riverdale-on-Hudson may 
be considered in counterview. The Flora of this section may be 
regarded as fairly representative of that of the Hudson Valley for 
some distance above New York City, and is far less southern in 
character than that of the coast region of New York and New Jersey, 
* Specimen too fragmentary for positive identification. 
