178 MONOGRAPHS OF NORTH AMERICAN RODENTIA. 
TaBLe XLVI.—Measurements of sixty-eight skulls of eastern and western specimens of ARVICOLA RIPARIUS— 
Continued. 
Widthat—| 2 | § | Underjawfrom | ¢ | 2 
= .2 tip or incisors to—| = Z 
S So ——— |) (os 5 
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be fe om 3 a cs = 
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oe Cd r) ° 9: Cl] ee 
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A SP isl ase oS Wee oer Sa ee iS Ble 
Racine, Wis ..-..------- 1.03 | 0.40 | 0.58 | 0.16 | 0.26 | 0.21 | 0.60 | 0.78 | 0.82 | 0.27 | 0.32 
Saint Louis, Mo......-- 1.04 | 0.42 | 0.62 | 0.17 | 0.26 | 0.18 | 0.61 | 0.78 | 0.80 | 0.27 | 0.31 
Secsed do ..--.-----..-----| 1.04 | 0.39 | 0.60 | 0.18 | 0.27 | 0.24 | 0.60 | 0.80 | 0.85 | 0.27 | 0.32 
seace do ......-.-.-.-----| 1.02 | 0.40 | 0.56 | 0.18 | 0.23 | 0.20 | 0.58 | 0.74 | 0.77 | 0.25 | 0.33 
Pec OCoConcoCobscecndeecsun 1.10 | 0.45 | 0.67 | 0.18 | 0.27 | 0.22 | 0.64 | 0.80 | 0.83 | 0.27 | 0.34 
Prairie Mer Rouge, La..|.--.-.|.----- 0.60 | 0.16 | 0.25 | 0.20 |.._... 0.76 | 0.79 | 0.25 | 0.30 
eae (i erdecotecescs ce-[eseee-|------) 0.62 | 0.15 0. 27 | 0:22 |......] 0.80 | 0.81 | 0.27 | 0.33 | 
Montorey, Cal .......... 1.00 | 0.40 | 0.62 | 0.15 | 0.25 | 0.17 |......|.----- eae ere eee montanus? 
secno: do ......--..-------] 1.12 | 9.41 |......| 0.16 | 0.30 | 0.18 | 0.62 | 0.€0 | 0.84 | 0.29 | 0.53 | edaz. | 
Petaluma, Cal...-....-.-. 1.13 | 0.44 | 0.69 | 0.14 | 0.30 | 0.23 | 0.66 | 0.81 | 0.85 | 0.30 | 0.35 | montanus? H 
San Diego, Cal ......--- | 1.16 | 0. 42 | 0.64 0.17 | 0.30 | 0.20 | 0.67 | 0.80 | 0.85 | 0.29 | 0.30 | edax. 
Upper Pit River, Cal. --.} 1.08 |.-.--.| 0.61 0.15 | 0.37 | 0.22 | 0.64 | 0.82 | 0.84 | 0.29 | 0.58 | longirostris. 
Lost River, Cal .......-. | 1.03 | 0.42 | 0.62 | 0.15 | 0.27 | 0.22 | 0.63 | 0.80 | 0.87 | 0.23 | 0.37 
Fort Tejon, Cal .--...-- 1.05 | 0.42 | 0.63 | 0.14 | 0.25 | 0.22 | 0.61 | 0.79 | 0.80 | 0.21 | 0.36 
Californiat-—c--- -c.. = 1.14 | 0.43 | 0.65 0.19 | 0.28 | 0.22 | 0.68 | 0.81 |.--.- 0.27 | 0.32 | californicus. 
Des Chutes, Oreg...---- 1.07 | 0.40 | 0.63 | 0.15 | 0.25 | 0.20 | 0.60 | 0.80 | 0.84 | 0.25 | 0.32 
Puget Sound, Oreg.-..-.. 1, 12 | 0.42 | 0.62 0. 18'} 0.27 | 0.21 |...--- 0.81 | 0.83 | 0.30 | 0.35 | occidentais. 
The blanks in the foregoing table are owing to the defective condition 
of certain specimens. The measurement of the length is made from the tip 
of the nasal bones to the upper border of the foramen magnum. The height 
is the perpendicular from the posterior corner of the last upper molar. The 
orbital width is at the point of greatest constriction of the orbit. The zygo- 
matic width is at the broadest point of the zygomatic arches. The molar 
series are measured from anterior corner of the first molar to posterior corner 
of the last one. The length of incisors is their protrusion from the aiveoli. 
The condyloid dimension is measured to the back corner of the condyle. 
The average length of the whole series is 1.08; the minimum ®* is 1.00 
and the maximum 1.20, the latter occurring in one of the ‘“breweri” speci- 
mens. ‘The variation is, therefore, 0.20, or about 20 per cent. of the mean. 
The average zygomatic width is 0.64; the maximum 0.69; the minimum 
0.55. The proportion of length to width is, therefore, as 1.0% to 0.64, 
or as 1.00: 0.59. The molar series in both jaws is about the same, and 
averages a little over 0.25 of an inch (from 0.24 to 0.30); the upper incisors 
protrude about 0.20 on an average (from 0.17 to 0.24); the under are rather 
wy “Of adult specimens: several young skulls, ranging from 0.80 to 1.00, are excluded from the 
e. 
