18 



NORTH AMEEICAN" FAUNA. 



[No. 37. 



History; Dr. Joseph Grinnell, of the Museum of Vertebrate Zoology, 

 University of Cahfornia; Mr. P. A. Taverner, of the Victoria Memorial 

 Museum; Mr. Ai^thur H. Heime, of MiUer Place, N. Y.; Mr. H. H. T. 

 Jackson, of the Biological Survey; and Mr. Edward K. Warren, of 

 Colorado Springs, Colo. 



EXPLANATION" OF CRANIAL MEASUREMENTS. 



Measurements of skulls of marmots, in millimeters, have been taken 

 as follows: 



Condylo-hasal length. — From posterior border of condyle to most 

 anterior point of premaxillae. 



Palatal length. — From posterior border of palate (disregarding 

 median process) to most anterior point of premaxillae. 



Postpalatal length. — From posterior border of palate to inferior lip 

 of foramen magnum. 



Length of nasals. — From most anterior point to most posterior 

 point. 



Zygomatic breadth. — Greatest breadth across zygomata. 



Breadth across mastoids. — Greatest breadth across mastoid processes. 



Least interorhital breadth. — Shortest distance across frontals in 

 front of postorbital processes. 



Breadth of rostrum. — Greatest breadth of rostrum at most anterior 

 points of maxillae. 



Maxillary tooth row. — Alveolar length of maxillary molar-premolar 

 tooth row. 



Genus MABMOTA Blumenbach.. 



Glis Erxleben, Syst. Regni Anim., I, 1777, p. 358 (part). (Not Glis Brisson, 1762.) 

 Marraota Blumenbach, Handb. der Naturgesch., I, 1779, p. 79. Type, Marmota 



alpina [=Mus marmota Linnaeus]. 

 Arctomys Scbreber, Saugthiere, 1780, Plate CCVIII. Type, Mus monax Linnaeus. 



GROUPS. 



The American marmots embrace three very distinct groups as 

 follows: (1) The monax group — all the eastern woodchucks, the 

 Canada woodchuck, the British Columbia v/oodchuck and the ochra- 

 ceous woodchuck of Alaska and northern British Columbia; (2) the 

 jlaviventris group — all the yellow-footed marmots; and (3) the cali- 

 gata group— the hoary marmots, including the species caligata, 

 olympus, and Vancouver ensis. The characters of the various groups 

 are given in connection with the technical descriptions of the species. 



A detailed study of Old World forms was not possible in the present 

 revision, but, so far as known, none of the Am^erican species has any 

 very near relative in Eurasia.^ Several groups are represented there, 

 some of the species resembling the caligata group in certain skull 

 characters, others apparently being more nearly related to the monax 



1 The species living in eastern Siberia has not been seen. 



