108 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 69 



RHEOMYS RAPTOR Goldman 



Panama Water Mouse 



[Plate 23, figs. 1, ia] 



Rheomys raptor Goldman, Smiths. Misc. Coll., Vol. 60, No. 2, p. 7, Sep- 

 tember 20, 1912. Type from near head of Rio Limon, Mount Pirre, 

 eastern Panama (altitude 4,500 feet). 



Rheomys raptor is a small member of the group which includes 

 Ichthyomys hydrobates and several rather aberrant genera of Murine 

 rodents. They are largely aquatic in habits and some species are 

 supposed to catch fish. In the present species there are short webs 

 between some of the toes, and the fringing bristles, together with 

 the character of the pelage, show fitness for an aquatic life. The 

 upper incisors are of a more generalized Murine type than those of 

 Ichthyomys which show specialization in form, the heavily beveled 

 internal border resulting in a deeply emarginate cutting edge adapted 

 for seizing and holding soft slippery prey. 



The specimens of R. raptor were all captured in traps placed in 

 the water among rocks and under logs in places where the water was 

 oozing or trickling out over the banks of a small creek, one of the 

 headwaters of the Rio Limon. There was no evidence that the 

 species preys on fish, but small collections of freshly emptied shells of 

 large water snails noted near the edge of the water in the vicinity 

 suggested another probable food supply. The snails had evidently 

 been gathered by some small predatory animal which had the power 

 to break through the shells. The point chosen for attack was in- 

 variably the middle of the largest whorl, which when perforated 

 exposed most of the snail's body. The holes in the shells were such 

 as might readily be made by the incisors of Rheomys. Stomachs 

 examined contained small quantities of pulp that may have been the 

 remains of the bodies of snails. 



Specimens examined: Mount Pirre (near head of Rio Limon), 3. 



Subfamily MURINAE. Rats 

 Genus RATTUS Fischer. Common Rats 

 In the genus are included the common rats which are cosmopolitan, 

 everywhere infesting the habitations of man, and many indigenous 

 Old World species. 



