188 THE MICHIGAN ACADEMY OF SCIENCE. 



NOTES ON THP: MOLLUSCS, REPTILES AND AMPHIBIANS OF 

 ONTONAGON COUNTY, MICHIGAN.* 



A. G. RUTHVEN. 



The collections, upon which this rejiort is based, were made by the 

 writer iu the Porcupine mountains during the mouth of September, 

 1903, for Mr. Bryant Walker. The collections from the vicinity of Lake 

 Gogebic were made by Mr. Walker in the summer of 1902. As far as we 

 know, no collecting had been done in Ontonagon county prior to 1902. 

 The collections made do not, of course, represent fully the fauna of this 

 region, as the time spent in the field was limited, but they add to our 

 knowledge of the distribution of the species listed. 



The Porcupine mountains are situated iu the western part of Onto- 

 nagon county in the northwestern part of the Upper Peninsula of Michi- 

 gan. From the south shore of Lake Superior, they rise 1,400 feet above 

 the level of the lake by a series of terraces which mark old lake beaches. 

 Owing to the close proximity of the mountains to the lake, the streams, 

 which have their origin on the north side of the mountains, have each 

 cut out, their owm channel down to the lake. Only those which head 

 on the farther slope unite to form the larger rivers, which are compelled 

 to flow around the mountains to find an outlet. As the streams have 

 their origin in mountain springs, their waters are clear and cold, and 

 their currents swift. They have cut deep gorges in the sandstone through 

 which they rush, leaving many little eddy pools among the projecting 

 outcrops on either side. Their beds consist almost entirely of solid sand- 

 stone, over which the3' flow except at their mouths where the currents 

 become sluggish and where silt is deposited forming a bottom of mud and 

 debris. The sluggishness of the rivers in the lower portions is due to the 

 formation of beaches across their mouths. These acting as dams, cause 

 the water of each stream to spread out into a small lake or pond. On 

 the edges of these ponds, the typical pond conditions are reproduced, as 

 is shown by the rushes and sedges, and a fauna of dragon fly larvae and 

 tadpoles. This gives rise to a curious mixture of pond and river condi- 

 tions, and a consequent intermingling of the faunas characteristic of such 

 habitats. 



Lake Gogebic lies to the south of the Porcupine mountains. The 

 southern boundary of Ontonagon county cuts it into approximately equal 

 halves. It is about fifteen miles long by a mile and a half wide. It 

 receives the waters of several streams, and is drained by the west branch 

 of the Ontonagon river. No attempt was made to sort the collections from 

 this vicinity. They are listed together as from Lake Gogebic. 



The forcvSt about the Porcupine mountains consists chiefly of hard- 

 woods and hemlocks, with an abundance of ferns in the moist places. 

 The lo.am about the roots of these ferns was found to be the most fav- 

 orable collecting ground for terrestrial molluscs, although many were 



* Contributions from the Zoological Laboratory of the University of Michigan, No. 85. 



