170 MICR0TIN.5; 



For external and cranial measurements, see tables at end of 

 volume. 



Remarks. — The material available comprises two or three 

 topotypes from the Bangs Collection and a fine series from 

 Ontario in the Miller Collection. Unfortunately our material 

 representing S. cooperi is very meagre. So far as the skull 

 and teeth are concerned, I can see no tangible difference between 

 S. fatuus and a specimen of S. cooperi from Brookeville, Indiana, 

 jjresented by Dr. Coues (No. 78.6.24.2) ; the skull of the latter, 

 however, is imperfect. 



3. Synaptomys (Synaptomys) helaletes Merriam. 

 (Synonymy under subspecies.) 



Range. — Kansas and Virginia. 



Characters. — Distinguished from *S'. cooperi externally by its 

 larger head and feet and longer tail, and by its larger and more 

 massive skull and teeth, much broader rostrum and more robust 

 mandible. Hmd-foot 19-20 mm. 



Two subspecies are at present recognized : — 



1. Colour as in *S'. cooperi; skull with shorter rostrum 

 and larger auditory bullae. 



S. h. helaletes Merriam, Virginia. 



2. Colour probably redder; skull with longer rostrum 

 and smaller auditory bullae. 



*S'. h. gossii Coues, Kansas. 



Dr. Merriam says (Proc. Biol. Soc. Washington, 10, p. 59) 

 that the difference in breadth and massiveness of rostrum, 

 mandible and upper incisors between helaletes and gossii "is so 

 great that skulls of the two require no comparison. Still, speci- 

 mens recently collected by V. Bailey in a sphagnum swamp near 

 Washington, D.C., are somewhat intermediate and indicate that 

 intergradation may exist." 



3a. Synaptomys (Synaptomys) helaletes helaletes Merriam. 



1896. Synaptomys helaletes Merriam, Proc. Biol. Soc. Washington, 

 10, p. 59. 



1897. Synaptomys cooperi stonei Rhoads, Proc. Acad. Nat. Sci. Phila- 

 delphia, 1897, p. 305. 



1912. Synaptomys helaletes helaletes Miller, U.S. Nat. Mus., Bull. 

 No. 79, p. 204, and " List," 1924, p. 394. 



Type. — U.S. National Museum. 



Type locality. — Dismal Swamjj, Norfolk County, Virginia. 



Characters. — Colour as in S. cooperi; toes usually partly 

 white. 



Skull and teeth larger, heavier and more massive ; zygomata 

 less strongly bowed outwards ; nasals broader posteriorly ; brain- 



