THE MOLL US KS OF THE ROCKY MOUXTALNS. 47 



Luis Valley to Mosca Pass through the Sangre de Cristo Range. This 

 alkali and sage-brush plain, fifty miles wide, is very far from being 

 " the garden of the world," as it has been styled. Near the eastern 

 side is a group ot" lakes, the water of which is highly alkaline. These 

 lakes are the abode and breeding-place of wild geese and ducks in the 

 greatest number, which are tormented without end by the gulls that 

 also make the lakes their home. On the gravelly beaches I picked up 

 many shells, and doubtless in the deep water many more species might 

 have been dredged, had there been time. But nowhere were there 

 any bivalves, except the little cyclades. The fact that there was no 

 lack of molluscan life in these intensely bitter waters was not surpris- 

 ing, since mollusks seem to flourish in mineral springs of both hot and 

 cold water everywhere. We had seen before a fine illustration of this 

 adaptation to j^eculiar conditions. The Grand River, which flows 

 through Middle Park, contains no mollusks at all that I could dis- 

 cover; but at Hot Springs, in a little lagoon filled at high water, 

 large, clear, ampullacea-Yike forms of the familiar Physa heterostropha 

 were common. Close by, in the few yards of exposed outlet of the 

 springs of hot sulphur-water from which the locality derives its name, 

 there occurred in the greatest profusion a blackish, globose variety of 

 the same species only one-fifth of an inch long. The temperature of 

 this water was at some points as high as 100 Fahr. In the basin of 

 a still hotter spring not ten feet away, whose waters were saturated 

 with chlorides of sodium and magnesium, hundreds of still smaller 

 Physoz were -floating about in mats glued together by a tangle of con- 

 fervoid vegetation and the depositions of the water. All these seemed 

 to have lost their apices by erosion, " which is extremely liable to 

 happen to shells living in water charged with alkaline salts other than 

 lime." On the other hand, quite as small and black were the examples 

 from the pure cold springs near Saguache, where there was seemingly 

 nothing whatever to stunt their growth. 



I was stimulated, by the results of my study of my own collection 

 from Colorado, to gather all possible information about the mollusks 

 of the Central Province generally, as it has been limited above. The 

 bibliography was quite large, but the notes of locality and station 

 very meagre. Tabulating the sum of the information open to me, 

 and including my own summer's work, I found that 138 nominal 

 species had been recorded as occurring in this inter-montanic region. 

 Of these, 49 were also Californian species; 15 occurred also in the 

 Eastern United States; 8 hailed from the Colorado Desert; 7 were 

 found all over the continent, and 8 all over the world ; and 3 belonged 

 in the Eastern Province, west ofuhe Alleghanies only. This left 47 

 nominal species, whese range, so far as yet known, is confined to the 

 Central Province. Many of the specific names in this list, however, 

 rest upon very insecure foundations, and will, no doubt, soon be re- 

 duced to synonyms. With respect to their vertical distribution, ob.- 



