NO. 2057. THE GRASSHOPPER MICE—HOLLISTER. 437 



measurements any of the skulls of other subspecies in the Imcogasier 

 group. The fronttil region is highly arched, the braincase is short 

 and broad, the interorbital region greatly constricted, and the 

 occiput elongated. (Plate 15.) 



Measurements. — Averages and extremes of three adult specimens 

 from North Dakota: Total length, 164 (160-168) millimeters; tail 

 vertebrae, 42 (38-47); hind foot, 22 (22-22); ear from notch in dry 

 skin, 14.0 (13.3-14.4). Skull: Condylobasal length, 27.4 (26.2-28.0); 

 zygomatic breadth, 16.2 (15.1-17.3); interorbital breadth, 4.6 

 (4.5-4.7); breadth of braincase, 13.3 (13.2-13.4); length of nasals, 

 11.4 (10.5-12.3); length of mandible, 16.7 (15.9-17.3); maxillary 

 tooth row, 4.5 (4.4-4.6). For detailed measurements of specimens, 

 see page 474. 



Ty ye- specimens. — Nothing is known of the later history of the 

 specimens on which Wied based his account of Ilypudaeus leucogaster. 



Remarks. — This subspecies reaches its extreme t^^pe of dark color- 

 ation in southeastern North Dakota, northeastern South Dakota, and 

 at Brown Valley, Minnesota. At some points in this region a few 

 specimens are partially melanistic. There are obviously only two 

 recognizable forms on the northern plains, the large pale subspecies 

 to the westward, missouriensis, and the large dark subspecies near the 

 eastern limits of the range. A good series of specimens from the type 

 localities of missouriensis, leucogaster, and pallidus, prove the distinct- 

 ness of the firet two and the identity of pallidus with true leucogaster. 

 Specimens from Fort Clark, the type-locality of leucogaster, are easily 

 nearest the dark form, are widely different in color from missouri- 

 ensis, and plainly represent the eastern race. The younger specimens 

 from Fort Clark are especially dark, like young from the Traverse Lake 

 region, and are quite different from the young of missouriensis. 



The whereabouts of the type-spocimen of Herrick's 0. I. pallidus 

 can not be ascertained. Prof. Charles E. Johnson, of the University 

 of Minnesota, writing under date of September 19, 1913, says: 



No one in the department seems to know what became of Herrick's material, whether 

 he took it with him when he left Minnesota or whether it has been lost or destroyed in 

 subsequent movings and shiftings in the department. 



Fortunately the collection of the Biological Survey contains four 

 topotype specimens of ^'pallidus," as well as other material from 

 near-by locahties. 



Specimens examined. — Total number 55, from the following 

 localities : 



North Dakota: Bottineau, 5 (Field Mus.); Devils Lake, 3; Fort 

 Clark, 18 (topotypes); Grace, 1; Hankinson, 8; Linton, 2; Minnewau- 

 kon, 1 (FieldMus.);Minot, 2 (Field Mus.); Pembina, 1 ; Sherbrooke, 1. 



South Dakota: Sisseton, 7; Traverse, 4 (topotypes of '^pallidus.'^) 



Minnesota: Brown Valley, 2. 



