MICHIGAN ACADEMY OF SCIENCE. 95 



Mr. Clarke had to cut them out in order to get what water he needed and the 

 beavers kept repairing them until the cranberries were harvested in the 

 late fall; the dams were then undisturbed. One dam examined was several 

 rods long and constructed across a brook that emptied into one of the ponds. 

 Clarke estimated the number of beavers on his four hundred acres at one hun- 

 dred. He stated that in the spring he frequently observed them in the drain- 

 age ditches, but that during the remainder of the year they remained in the 

 ponds. Since January, 1913, the beaver have been nearly exterminated in 

 the ponds about Vermilion, and in 1914 the writer found only skulls and 

 decaying carcasses. A skin and skeleton of an adult female weighing 41 

 pounds was secured in 1912, and several skulls in 1914. An adult female, 

 taken near Vermilion in 1913-14, was said to have weighed 68 pounds, and, 

 according to residents, another, taken a few miles west of Vermilion in the 

 winter of 1914, weighed 71 pounds. 



11. Mus musculus (Linn.). House Mouse. — This species s common about 

 the buildings of the settlers. 



12. Peromyscus maniculatus gracilis (LeConte). Michigan Mouse. — The 

 Michigan mouse was found in abundance on the wooded sand dunes and 

 on the sand of the beaches to near the water's edge. It was also taken 

 about the cranberry house of John Clarke at Vermilion, and in winter is 

 said to often become quite troublesome about the buildings. It also occurs 

 in the beech-maple forest. In the wooded areas it lives in old logs and 

 stumps and no doubt also in hollows of standing trees. 



13. Evotomys gapperi (Vigors). Red-backed Mouse. — This species occurs 

 in the heavy forest near Vermilion, where several were trapped in July and 

 August, 1914. 



14. Microtus pennsylvanicus (Ord.). Meadow Vole. — This species is com- 

 mon in suitable habitats — the meadows or cranberry marshes and about 

 ponds and lakes — where they do some damage by cutting open the cran- 

 berries (no doubt for the seeds.) Mr. House stated that when these marshes 

 are flooded in order to gather the berries, he usually sees numliers of this 

 species aliout the sod dykes, also running about the marsh and sometimes 

 swimming. In 1912 the writer saw one on the bank of the Shelldrake River 

 south of Vermilion, and trapped twelve at the edge of Little Lake in an 

 area less than two rods square, and in 1914 took several about East Ver- 

 milion Lake. 



15. Ondatra zibethica (Linnaeus) . Northern Muskrat. — This species is not 

 rare in the region studied although not as common as in southern Michigan. 

 A few lived in the dykes about the cranberry marsh at Little Lake, and it 

 was quite common about the beaver ponds at Vermilion. These animals are 

 also seen occasionally on the beach near the outlets of streams and ditches. 

 They are not protected from the trappers, as they do some damage to the 

 dams and embankments which control the water on the cranlierry marshes. 

 It is much trapped and particularly recently on account of the high price 

 of its fur. 



16. Zapus hudsonius (Zimm.). Northern Jumping Mouse. — This was the 

 only jumping mouse found. A male and four females were trajiped at 

 Little Lake in 1912, and three specimens were taken at Vermilion in 1914. 

 Of the latter, two Avere found dead and the third, an immature male, was 

 caught on the beach west of Vermilion, in a dense growth of beach grass and 

 wild pea vines. 



17. Erethizon dorsatum (Linn.). Canadian Porcupine. — This species is 

 rather common and was found in all of the terrestrial habitats. It was oc- 



