122 BULLETIN 99, UNITED STATES NATIONAL MUSEUM. 



Genus DASYMYS Peters. 



1875. Dasymys Peters, Mon.-ber. K. Preuss. Akad. Berlin, 1875, p. 12. (D. 

 gueimii.) 



The swamp rats of the genus Dasymys are animals which do not 

 seem to be common in collections. At least our collectors failed to 

 take them in such satisfactory series as usual with many other 

 murines. Wlien collections are made throughout eastern and central 

 Africa and it becomes possible to monograph the group in a satisfac- 

 tory manner, most of the forms listed below will doubtless prove 

 to be geographic races of Dasymys incomtus Sundevall. 



For measurements of specimens see page 124. 



DASYMYS HELUKUS HELUKUS Heller. 



Plate 33. 



1910. Dasymys helukus Heller, Smithsonian Misc. Coll., vol. 54, [No. 1924], p. 2. 

 February 28. (Sirgoit, Guas Ngiahu Plateau, British East Africa; type 

 in U. S. Nat. Mus.) 



1910. Dasyvius helukus Roosevelt, African Game Trails, Amer. ed., pp. 473, 



478;Londoned.,pp. 485, 490. (Part.) 



Specimens. — Fifty-five, from localities as follows: 



British East Africa: Kaimosi, 50, including 9 in alcohol (Heller) : 

 Ejbabe, Kisumu, 1 (Heller); Nzoia River, 1 (Heller); Sirgoit, 3, 

 including 1 in alcohol (Heller). 



The skins in this series are remarkably uniform in color. Heller 

 notes three sucking young with a female collected at Kaimosi, January 

 29. 



DASYMYS HELUKUS SAV ANNUS Heller. 



Plate 34. 



1911. Dasymys savannus Heller, Smithsonian Misc. Coll., vol. 56, No. 17, p. 14. 



February 28. (Fort Hall, British East Africa; type in U. S. Nat. Mus.) 



Specimens. — Fifteen, from the following localities: 

 British East Africa: x\rcher's Post, 1 (Heller); Fort Hall, 1 

 (Loring) ; Isiola River, 1 (Heller) ; Kapiti Plains, 1 (Loring) ; Lakiundu 

 River, 3 (Heller) ; Mount Kenia, west slope, 8, including 6 in alcohol 

 (Heller, Loring). 



The material representing this pale reddish form is far from satis- 

 factoiy. I suspect that more specimens will show the ad visibility 

 of separating a new subspecies from north of Mount Kenia. No 

 specimen in the series matches the type in color or skull chaiacters, 

 but some of the skins from the Lakiundu River are the extremes of 

 reddish coloration. The males in this small series are all of a grayish 

 brown, much as in males and females of true lielukus, while the females 

 are all of tlie reddish tjx>e. The material is hardly extensive enough 

 to prove that tliis is a regular sexual coloration. In other forms the 

 sexes are indistinguishable in color. 



