52 DR. wocHERER ON THE [Jan. 27, 



Bibron make no allusion to this character in C. atrox. Now all the 

 specimens of C. atrox which I have had occasion to examine have 

 seven upper labial shields. Only one has oq one side eight, which 

 must be considered an irregularity. 



Dr. Gray describes C. brasiliensis as having nine or ten upper 

 labial shields, the hinder ones of which are smaller ; Schlegel de- 

 cribes it as having nine ; and Dume'ril and Bibron do not mention 

 the number of labial shields at all. 



The three specimens differing from those of C. atrox mentioned 

 above have all eight upper labial shields on each side, the last one 

 narrower than the last one in C. atrox. 



A statement I made in my former paper, that my specimens of C. 

 atrox differed from those described by herpetologists in having fewer 

 longitudinal rows of scales, I now take the opportunity to rectify. 

 The number of longitudinal rows of scales in the species of this genus 

 is not always mentioned as a specific character, and indeed it does not 

 appear very serviceable as such. Schiegel's C.jararaca, the C. bra- 

 siliensis of Dr. Gray's catalogue, has twenty-seven rows of scales ; 

 of C. atrox he says (Essai, ii. p. 536), "On compte quelquefois 29 

 rangees d'e'cailles," leaving it perhaps hence to be inferred that it has 

 generally a lesser number, or twenty-seven, like the one just de- 

 scribed, which is C. brasiliensis. Dumeril and Bibron (vii. p. 1509 

 and p. 1511) give to C. atrox from twenty-nine to thirty-two, to 

 C. brasiliensis twenty-seven rows. All my specimens of C. atrox, 

 with few exceptions, have twenty-seven rows of scales, a few having 

 twenty-five. Of the three specimens differing from them, two have 

 twenty-five and one twenty-three rows of scales. 



Schlegel, Dume'ril, and Bibron draw some specific differences from 

 the shape of the head, the former saying (ii. p. 535) that the snout 

 of C. atrox is more conical, by which I suppose is meant more 

 rounded, Dumeril and Bibron stating that the sharp edge on the 

 anterior part of the head is almost effaced, and does not reach back 

 to the orbits, furthermore that the scales on the anterior part of the 

 head are comparatively much larger than on the posterior part in C. 

 brasiliensis ; but all these differences do not appear very striking in 

 Schiegel's excellent figures on plate 19 of the 'Essai.' My three 

 specimens distinct from C. atrox would rather agree in these points 

 with the descriptions of C. brasiliensis of these authors. 



Schlegel points to the larger size of the superciliary and superior 

 labial shields in C. atrox, to its larger and more numerous mental 

 shields, to the stronger keel on its scales, showing a strong tendency 

 to take the form of a tubercle, by which I understand that it is 

 higher and shorter, not reaching the tip. Now these characters, if 

 they occurred simultaneously, might very well serve as some of the 

 specific characters ; and it does not appear just in Dumeril and Bi- 

 bron to say (vii. p. 1508), " M. Schlegel, dans I'embarras on il s'est 

 trouve, n'a indique que des differences peu importantes, tirees de la 

 forme des ecailles dont la carene parait plus forte ; des lames noires 

 alongees, on de I'etendue relative des plaques surciliaires ainsi que les 

 plaques labiales," — although they confess their inability to suggest 



