ZOOLOGY REPTILES. 3 



Char. 2. The head is depressed^ covered with horny scutellae ; marginal scutes 23-27, those 

 of the sternum 11-12. 



Char. 3. The skull is generally depressed and solid, with a distinct bony margin, and covered 

 with horny plates ; the dorsal plates 13 with twelve pairs of marginal plates, the caudal j)air 

 being separated by a distinct suture; nuchal plate narrow. The sterno-costal commissure is 

 generally long, and usually furnished with a distinct and rather large axillary and inguinal 

 plate. The sternum has 11 or 12 shields, the gular pair being sometimes united, but never 

 having an extra plate between them as in Ghelydae. 



Char. 4. Live in ponds and ditches ; only take their food when in water ; eggs oval and 

 white; motions rapid ;" living on mollusca, worms, insects, and carrion; inhabit warm and 

 temperate climates. — (Gray.) 



EMYS, Brogniart 

 EMYS 'NIGEA, Nob. 



Sp. Char. — Shell oblong-ovate, slightly compressed at the sides, and emarginate, but not 

 distinctly serrated posteriorly ; latero-posterior margins of carapax everted ; nuchal plate 

 narrow, truncate anteriorly, broader posteriorly ; 24 marginal plates, the two posterior more or 

 less quadrilateral, the two adjoining pentagonal ; color blackish above, the upper part of head 

 and neck presenting numerous very small yellow spots upon a black ground ; anterior extremi- 

 ties with a tinge of yellow ; under jaw and tliroat yellow, witli dark colored markings ; plastron 

 yellow in the middle, with large blotches of black or dark brown at the sides, and anteriorly 

 and posteriorly ; under surface of tail and extremities blackisli ; tail of moderate length. 



Dimensions. — Length of head, 1 inch ; breadth, ^ ; length of carapax, 6| inches, measured 

 along curvature superiorly ; breadth at middle, 5| inches ; of tail, 2^. 



Habitat. — Posa creek, southern part of Upper California, where it is very abundant. 



Gen. Obs. — This species resembles none of the North American Emydes with which I am 

 acquainted. Its dark color puts one in mind of, but is not so jet a black as that of Sternothaerus 

 niger of Madagascar. 



