266 PROCEEDINGS OP THE ACADEMY OF 



159. D. p a v o n i n a Cuvier, MSS., Schlegel, Essai, ii. p. 280. Leptognatkus 

 pavoninus Dum. & Bibr. vii. p. 474, Giinther, I.e. 179. 



One specimen, S. America. ? 



160. D. b re vi s nobis. Leptognatkus brevis Dum. & Bibr. vii. p. 476. 



One specimen. Cocuyas de Veraguas, New Grenada, R. W. Mitchell. 



Oar specimen of this rare species has but one preocular plate ; its form too. 

 is no less slender than that of our D. pavonina, which, however, may 

 not be fully grown. Otherwise it coincides with the description cited. The 

 dark brown of the upper surface of the head is marked with small, irregular 

 spots of white. 



Sibon Fitzinger. Type S. a nn ul at a . 



Neue Classification der Reptilien, 1826, p. 60. Leptodeira Fitz., Systema 

 Reptilium, 27, 1843. Giinther, Cat. Brit. Mus. p. 165. 



161. S. annulata Fitz. 1. c. Coluber annulatus Linn. Dipsas annulata 

 Schleg. Essai, ii. p. 294, Dum. & Bibr., vii. 1141. Leptodeira annulata Fitz. 

 et Gthr. 1. c. 



Scales in nineteen or twenty-one rows. 



a. With an undulating dorsal band. Var. A. Dum. & Bibr. 



Six specimens. Surinam, Dr. Hering. 



b. With isolated, sometimes geminate spots. Var. B. Dum. & Bibr. 



Five specimens. Caraccas, Mr. Ashmead. 



One ' " " W. G. Bolton. 



One " Isth. Panama. Dr. LeConte. 



Four " S. America, Mr. H. Cuming, in ex. 



Scales in twenty -three rows. 

 Two specimens. Honduras, J. S. Hawkins & Dr. LeConte. 



One " Near Volcano Isalco, San Salvador, Capt. John M. Dow. 



One " Xalapa, John Cassin, Esq. (De Oca coll.) 



Two ' ? ? 



There is much difference in the appearance of the specimens of this species 

 which come from the extreme points of distribution represented in our collec- 

 tion, viz. Surinam and Xalapa. As has been observed by authors, those from 

 the more southern localities, have more slender bodies and tails, and hence, 

 fewer longitudinal rows of scales, and the head is more distinct. The whole 

 ' physiognomy" is more that of the arborial Dipsadiens. This is more striking 

 in a specimen where the vertebral rows of scales in places is slightly, but dis- 

 tinctly larger than the others. From the Stomach of a Surinam specimen we 

 took an adult Hyla ; from one from Caraccas, a Thecadachylus rapicaudus. 



Specimens from Mexico exhibit a stouter, heavier form of body, a greater 

 number of longitudinal rows of scales, and a shorter tail. They seldom, if ever, 

 have the dorsal spots confluent into a band, strictly speaking, as in the var. A. 

 Dum. & Bibr. Their aspect is that of a terrestrial species. 



That these forms are really distinct species, is possible, but it could only be 

 demonstrated with large series of specimens from carefully ascertained locali- 

 ties, if at all. Some of the specimens from Caraccas and Panama, are very 

 intermediate as respects the peculiarities mentioned. 



Dipsas septentrionalis Kennicott, (Mexican Boundary Survey, ii. 

 Reptiles, p. 16, pi. viii. fig. 1,) belongs to this genus. The grooving of the 

 posterior upper maxillaries is not represented in the fig. 2, pi. 22, 1. c. It 

 seems to resemble northern forms of S. annulata; but has the nasals and 

 prefrontals differently proportioned, etc. It has three preoculars but we not 

 'infrequently find one or more supplementary preoculars in the annulata. 



[June, 



