THE NAUTILUS. 105 



FOSSIL AND LIVING SHELLS FOUND IN LITTLE MUD LAKE, WESTMAN- 

 LAND, AROOSTOOK COUNTY, MAINE. 



BY OLOF O. NYLANDER. 



This small lake is located in the forest near the south line of 

 Westmanland Plantation, and is the headwater of Salmon Brook. 

 This little lake contains some interesting shells not (bund in the 

 county before. The deposit of dead shells (marl) is many feet in 

 thickness, and is chiefly composed of Pisidia. 



The living shells are extremely rare in the lake, and those col- 

 lected came from small spring brooks at the north end of the lake. 

 Dr. V. Sterki has kindly examined all the Pisidia. I do not know 

 what the amateur collectors would do with these miserable little 

 shells without his assistance. The fossils collected are as follows: 



Lymniza desidiosa Say. Common. 



Planorbis campanulatus Say. Common. 



Planorbis bicarinatus Say. A few young shells. 



Planorbis hirsulus Gld. One specimen. 



Planorbis parvus Say. Abundant. 



Ancybts parcillelus Hald. One specimen. 



Valvata sp. ? A variable species; some are nearly flat, others 

 have the apex extremely elevated, a large percentage are decollate 

 and the whorls are sometimes dislocated near the apex. 



Mr. Bryant Walker has examined specimens and states: "They 

 are extremely curious * * * I have never seen any like them before. 

 They are no doubt a form of V. sincera Say." 



Dr. W. H. Dall gives me the following information: "They are 

 exactly like the depauperate form of V. lewisii Currier. * * * The 

 distortions are familiar to me as found in marl deposits, the water 

 becoming too much mineralized for the mollusks." 



I made special efforts to obtain living specimens of this Valvata 

 during the two trips to the lake, but not one could be found. 



Anodonta fragilis Lam. Fragments. 



Sph&rium sulcatum Lam. A few valves. 



Sph cerium rhomboideum Say. Common. 



Musculium sp. ? probably securis Prime. Small. 



Pisidium variabile Prime. 

 " compressum Prime. 

 " affine Sterki. 



