642 NORTH AMERICAN SNAKES COPE. 



Of seventeen specimens exaiuinetl, seven have the superior labials 

 8-9; eight have 8-8; and two have 9-9. Four have twenty-nine rows 

 of scales; ten have thirty-one rows; one has thirty-three; and one has 

 thirty-five (No. 2243). The number of spots on the body is very varia- 

 ble. One has thirty-six dorsal sj)ots (No. 154G) ; one has fort3'-six (No. 

 1532); seven have between fifty and sixty; four have between sixty 

 and seventy ; and four liave over seventy, the highest being seventy- 

 nine (No. 181(3). The specimen (No. 5741) on which the P. wilkesii Bd. 

 and Gird., was founded is abnormal in the nondivision of the pre- 

 frontal scuta; the only example I have observed in the genus. 



The range of this species is coterminous with the Pacific region, ex- 

 tending from San Diego on the south to Puget's Sound on the north. 

 It is found in the Mohave Desert, and at Pyrmout, Nevada (8139). 

 Northward it extends to eastern Oregon and to Walla Walla, Wash- 

 ington. 



Pityophis vertebralis Blv. 



Duuierilet Bibron, Erp. Gon., vii, 1854, p. 238; Cope, Check List Batr. Rept. N. Amer., 



187.5, p. 39 ; Bull. U. S. Nat. Mii8., 3'2, 1887, p. 7-2. 

 Colnher vertebralis Do Blv., Nouv. Ann. Mus. Nat. Hist., Paris, iii,ldo4, p. Gl, PI. xxvii, 



FigH. 2, 2a, 2b: Bd. aud Gird., Cat. Serpt. N. Auier., 1853, p. 152. 

 PtUjopMs hamtatois Cope, Proc. Acad. Phila., i860, p. 342. 



ntiiophis melanolcKciis var. vcrlebraJis Blv., Jan, Icon. Gcu. Olid., ii, 22, i, fig. 3. 

 Peninsula of lower California. 



HETERODON lieanvais. 



In Latreilie's Hist. Nat. des Reptiles, iv, 1799, p. 32. 



Dutueril et Bibrou, Erpetologie Generale, vii, 1854, p. 76G ; Bd. and Gird., Cat. Serpt. 



N. Amer. 1853, p. 51; Giiuther, Cat. Colubr. Serpt. Brit. Mus., 1858, p. 82; Cope, 



Bull. IT. S. Nat. Mus., 32, 1887, p. 54. 



Dentition diacrauterian. Caudal scutella divided ; anal plate double. 

 Kostral plate recurved, with transverse upturned edge and flat antero- 

 inferior face. The nine cephalic plates, a loreal, two nasals and ocular 

 plates, present. Scales keeled. Form robust. Pupil round. 



The few species of this genus which are known agree also in hav- 

 ing a series of scales separating the eye from the superior labial plates, 

 and in having an azygos plate behind the rostral. The posterosni)erior 

 aspect of the rostral plate has a keel on the midtlle line, and there are 

 from three to five, generally four, scales in the first temporal row. The 

 tail is short. The anterior ribs are capable of extension so as to flatten 

 that part of the body, as is done by the cobras of the genus Naja, but 

 the expan.sion is not so wide, and it has greater longitudinal extent. 

 The postgeneil plates are reduced to a very small size, and are sep- 

 arated from each other by small scales. 



The species of this genns ranges throughout North America except- 

 ing the Pacific rej^ion. They do not extend far into the Sonoran, and 

 are absent from the Lower Californian and the ^Mexican regions. They 

 have no representatives in equatorial America or the West Indies, but a 



