14 University of California Puhlications in Zoology [Vol. 21 



defined crests which may or may not unite with lambdoidal ridge 

 superiorly. Basioccipital with well defined median ridge. Auditory 

 bullae moderate in size, rounded internally, and abruptly sloping from 

 inner margin to outer, but strongly depressed in region below meatus. 



Palate with shallow palatine sulci, but with median ridge flattened 

 and depressed. Lateral pits fenestrated. Interpterygoid fossa nar- 

 row, though pterygoids and hamular processes diverge posteriorly. 

 Posterior palatine foramina present and wide open. Incisive foramina 

 long, the outer sides nearly parallel throughout their length, though 

 in some specimens the foramina are slightly expanded near middle. 



Zygomatic arches diverging rapidly anteriorly, with region of 

 greatest convexity slightly posterior to end of maxillary root. Jugal 

 somewhat expanded anterior to middle, abruptly tapering anteriorly 

 and mortised into maxillary root of zygoma. Zygomatic arches but 

 slightly notched at anterior junction with premaxillae. 



Mandible light, with convex inferior profile ; relatively deeper than 

 in calif or niciis. Ridge for masseteres laterales normally well de-' 

 veloped. Coronoid process slender, its base variable in width, its 

 extremity rising above level of condyle and curved backward at tip. 

 Angular process light, curved outward, but not. extending posteriad 

 to plane of condyle. Peripheral tuberosity over base of incisor present 

 but not conspicuous. Base of mandibular foramen considerably above 

 level of cutting surface of last molar. Mental foramen situated on 

 lateral face below superior surface of diastema. 



Teeth. — In general the teeth are like those of calif ornicus, but 

 can be immediately distinguished from the latter by the smaller size 

 of the molars. Anterior loop of M^ decidedly concentric. An internal 

 lobe normally present on posterior triangle of M-. Long terminal 

 loop of M- subtended externally by slight notch and internally by a 

 deep reentrant angle ; the indentation of loop by deep reentrant angle 

 imparts to it a strongly curved crescentic outline. Inner side of pos- 

 terior limb of long terminal loop occasionally with slight indentation. 



Most triangles of lower molars show an exaggeration of the ten- 

 dency to flattening characteristic of californicus. Anterior loop of 

 My usually more deeply indented than in the latter. Transverse 

 diameter of jDosterior crescentic loop usually relatively wider. 



Remarlis. — The distribution of this race has not been satisfactorily 

 worked out. Specimens from Olema are apparently intergrades be- 

 tween eximius and aestuarinus. Around San Francisco Bay, on the 

 north side, aestuarinus occupies a narrow coastal strip, and inter- 

 gradation between eximius and aestuarinus may take place at any 

 point where conditions are suitable. Eximius occurs mainly in the 

 Transition zone. Specimens reported from Cassel, Shasta County 

 (Bailey, 1900, p. 35), if they belong to this race, must have been 

 collected in the Upper Sonoran zone. 



