1915.3 



INTRODUCTION. 



19 



SEASONAL VAEIATION. 



Winter pelage of most moles is slightly darker than that of summer. 

 No other seasonal variations occur except in Condylum: The tail of 

 Oondylura during the summer months is narrow and elongate ; during 

 the winter months it becomes much thickened, abruptly constricted 

 at the base, and tapered apically. Both males and females have 

 been found with tails in both conditions. The variation probably is 

 due to assimilation of fat. Enlargement of the tail may begin as 

 early as August, but usually it does not begin until September, or 

 possibly later; the maximum size is reached in most cases by the 

 latter part of November and is retained until March or April, when the 

 tan gradually diminishes to its minimum summer size by the last of 

 May or the middle of June. 



EXPLANATIONS. 



EXTERNAL MEASUREMENTS. 



External measurements of moles are in milhmeters and, unless 

 otherwise stated, are those made by the collector from the animal 

 in the flesh. The following have been used: 



Total length. — Tip of nose to end of terminal tail vertebra. 



Tail vertebrse. — Base of tail at upper surface to end of terminal tail 

 vertebra. 



Hind foot. — Heel to end of longest claw. 



CRANIAL MEASUREMENTS. 



Cranial measurements were made by the author with a vernier 

 caHper. The following have been employed: 



Greatest length. — Antero-posterior diameter of skuU from anterior 

 median point between bases of first upper incisors to most posterior 

 point of supraoccipital in median line. 



Palatilar length. — ^Antero-posterior diameter of palate from poste- 

 rior median point between bases of first incisors to posterior median 

 border of palate. 



Mastoidal 'breadth. — Lateral diameter of skuU measured through 

 mastoids. Greatest lateral diameter of skull. 



Interorhital breadth. — Lateral diameter of cranium measured at 

 coronal suture. 



Maxillary tooth row. — Antero-posterior diameter of upper molar- 

 premolar row measured at alveolar border. 



Mandibular molar-premolar row. — ^Antero-posterior diameter of 

 lower molar-premolar row measured at alveolar border. 



The bone immediately anterior to the iambdoidal crest and just 

 posterior to the parietals is here called the ' 'interparietal." This 

 bone in moles has been considered by some writers part of the supra- 

 occipital. 



