138 Proceedings of the Biological Society of Washington. 



Cranial characters. — Old male (the type): Skull peculiar and distinc- 

 tive ; size large (basal length 357 mm.); skull long, narrow, high and 

 strongly dished; frontal shield highly elevated, rising abruptly from 

 rostrum, rather broad, deeply sulcate throughout medially, swollen over 

 orbits ; short-pointed posteriorly ; orbits nearly vertical ; postorbital pro- 

 cesses small and strongly decurved ; fronto-nasal region sulcate and 

 strongly dished; rostrum rather short and narrow; nasals horizontal 

 except posteriorly, where they rise strongly; braincase exceedingly long; 

 sagittal crest high posteriorly, straight, and long, reaching anteriorly to 

 halfway between parietals and plane of postorbitals ; zygomatic arches 

 moderately spreading, subtriangular (not outbowed), expanded verti- 

 cally ; palate and postpalatal shelf relatively long and narrow for so large 

 a skull; postpalatal notch rather narrow and short; occipito-sphenoid 

 long (about 103 mm.); mastoids outstanding; anterior nares rather 

 small, subtruncate and broader than high in type skull, higher and 

 less truncate in the Iliamna skulls. Lower jaw absent in type specimen. 

 But in an old male from Iliamna, on north side of Cook Inlet (No. 

 209885) which closely matches the type, the ramus is broadly flattened 

 vertically, much broader posteriorly than anteriorly; coronoid blade 

 high and rather vertical. In younger skulls from Iliamna the eoronoid 

 is broader basally and less high. Canines large and massive; molars 

 moderate ; M'' large in the type, smaller and more cut away on outer side 

 of heel in the Iliamna specimens. No. 209885 from Iliamna agrees with 

 the type except that the nares are higher and less truncate, and the last 

 upper molar smaller, with heel more cut away on outer edge. 



Skull of old female (No. 209881) from head of Chitina River (80 miles 

 from McCarthy), Alaska, collected by Capt. J. P. Hubrick: Size medium; 

 cranium moderately arched; frontal shield broad, deeply sulcate anteri- 

 orly, strongly swollen over and posterior to orbits, the point lyrate and 

 reaching parietals ; postorbitals rather large, blunt, and somewhat de- 

 curved; fronto-nasal region strongly dished and depressed medially; 

 rostrum rather large and high, nearly horizontal; palate and postpalatal 

 shelf broad; postpalatal notch moderate and rather broad. Lower jaw 

 long; coronoid blade high and rather narrow, its apex only slightly re- 

 curved. Dentition light ; canines small and short ; molars rather narrow, 

 apparently normal (too badly worn to admit of description except that 

 the heel of M' is moderately long and rather broadly rounded pos- 

 teriorly ) . 



Cranial comparisons. — Old male cressonus (type) compared with old 

 male dalli : Size about same ; vault of cranium and frontal shield much 

 more elevated, less flat, less horizontal, and much more swollen over 

 orbits; shield more deeply sulcate; postorbitals weak and decurved [in 

 dalli larger and more horizontally outstanding]; fronto-nasal region 

 more strongly dished ; rostrum narrower and longer ; zygomata much 

 less widely outstanding and much less bowed ; palate longer ; molars very 

 much larger. 



Old male cressonus (type) compared with adult male nuchek (type): 

 Size, elevation of vault of cranium, and zygomatic breadth about same; 



