104 THE NAUTILUS. 



Mission Mountains as high as 3800 ft., in the ponds bordering Flat- 

 head Lake, and in Swan Lake. 



Estey's pond covers some 10 or 15 acres, three miles from the 

 Biological Station, and a mile from Flathead Lake. In August, 

 1900, the shores of this pond were literally covered with dead shells, 

 and great quantities of live ones in the water. 



It was here that a very interesting experiment was performed with 

 these shells and a large frog. A dead shell was tossed in front of 

 the frog, close to his nose. The shell was immediately seized, and 

 an unsuccessful attempt made to swallow it. It was disgorged by 

 the aid of the fore feet. A second attempt gave the same result. 

 This was continued until the frog had seized the eighteenth dead 

 shell, when he seemed to weary of the sport, and took a rest. After 

 this he would seize only now and then, and only those in easy reach. 

 After the 23d shell had been seized he no longer made any effort, 

 and a good sized pile of shells was made with no result. Other at- 

 tempts on other frogs gave practically the same result, with a slight 

 variation in the number. 

 Planorbis parvus Say. 



In August, 1897, while camped on the bank of the Pend d' Oreille 

 river a couple of miles below the outlet at Flathead Lake, some sand 

 siftings produced a dozen or more of these small shells. 

 ( To be contimied.) 



THE SHELL-BEARING MOLLUSCA OF RHODE ISLAND. 



BY HORACE F. CARPENTER. 



[Continued from page 96. ~\ 

 203. Modiolus modiolus Linne. 



Mytihis modiolus Linn., Wood, Don. Chem., DeKay. Modiola 

 modiolus Tint., Gld., Perkins, Dall. 



Shell large, thick and solid, oblong-ovate ; beaks at the anterior 

 end which is narrow ; posterior broad, rounded ; hinge margin 

 straight, ascending from the beaks at an angle of forty-five degrees 

 to the centre, then curving downward to the posterior end; basal 

 margin arched a little upwards near the centre, gaping at this point 

 for the passage of a byssus ; epidermis dark brown, thick, folding 



