Poisonous snakes of north America. 



407 



Fig. 43. 

 HEAD OF AQKISTRODON 

 PISCIVORUS FROM 



ABOVE. 



(After Baird. ) 



Description.* — No loral. Inferior wall of orbit constituted by third 

 labial: 25 dorsal, rows. Dark cliestimt browu, with indistinct vertical 

 dark bars. Line from superciliary along the edge of the head, through 

 the middle of the second supralabial row. A second line from the 

 lowest point of the orbit parallel to the first (figs. 43 and 44). 



Scales all large and well developed; those on the sides and back of 

 head conspicuously so. Two nasal plates, with the nostril between 

 them. Anterior orbitals 2, one above the other, the 

 upper extending from the eye to the posterior nasal, 

 the lower linear and forming the npper Avail of the 

 pit. Lower and posterior wall of pit constituted by 

 a narrow plate resting along the third labial and ter- 

 minating on the second. Third labial very large, 

 constituting the inferior wall of the orbit, of which 3 

 scales form the posterior. Upper labials 8, very large 

 and broad; lower 10. Occipitals [parietals] terminated 

 each by a triangular plate. All the scales on the 

 back of the head carinated. Dorsal scales all cari- 

 uated. 



General color, dark chestnut-brown with darker 

 markings. Head above, purplish black. An obsolete 

 chestnut-brown streak ])asses from the posterior end of the superciliary 

 along the npper edge of the head, through the middle of the second row 

 01 supralabial scales. A narrow yellowish white line passes from the 

 third labial, or begins just below the lowest part of the orbit, and pass- 

 ing backward parallel with the first stripe crosses the angle of the mouth 

 at the seventh labial and meets the first stripe on the side of the neck, 

 where it is confiuent with yellowish white of the throat. On the lower 

 labial are 3 short, nearly vertical, light bars; on fourth, sixth, and 

 seventh, the rest of the Jaw itself, as well as the interval between the 

 stripes on the sides of the head, dark purplish brown, of which color is 

 also the space in front and below the eyes. General color above, dull 



dark chestnut-brown. On each side a series 

 of 20 or 30 narrow, vertical, purplish black 

 bai s 1 or 2 scales wide. Of these, sometimes 

 2 contiguous to each other on the sametsideare 

 united above into an arch, inclosing a space, 

 the center of which is rather duskier than the 

 ground color; at others, corresponding bars 

 from the opposite sides unite and form half rings, encircling the body. 

 Sometimes there is a lighter shade bordering the dark bars. Beneath, 

 black, blotched with yellowish white. 



Number of veutrals [gastrosteges], 130 to 145; of subcaudals [uro- 

 steges], 39 to 45, of which divided, to 21. 



Fig. 44. 



SAME FROM SIDE. 



*By 8. F. Baird, iu JJaird aud Guard's N. Am. Serj)., p. 19. 



