NATURAL SCIENCES OF PHILADELPniA. 53 



top of the head, although having a general resemblance, differ in fact from the 

 corresponding plates of smaragdinus ; the nostril, instead of being between two 

 nasal plates, (the naso-rostral and naso-frenal,) is situated between the naso- 

 rostral and the frenal, which, however, may be accidental ; the frenal plate is 

 considerably less narrow ; the eyes, instead of being oval, as in smaragdinus, 

 are round or subround, and much more prominent ; the temporal plates are five 

 in number, in two longitudinal rows, three in the inferior and two above ; in 

 smaragdinus there are four, two below and two above ; in another, younger 

 specimen, four on one side, three on the other, but differently arranged ; the 

 number of superior labials is the same in each, viz., nine, the fifth and sixth 

 immediately beneath the eye; but the shape of these plates diflVrs in the two 

 animals, no two being alike; the posterior and superior angle of tne sixth in 

 smaragdinus is much more prolonr;ed upward and backward, and the seventh is 

 much larger ; the middle labial and the accessory labials differ in form, but the 

 difference most to be remarked is between the posterior geneials, which in smarag- 

 dinus are very long and comparatively slender ; the scales in the one snake are 

 long, narrow, and strongly carinated, in the other perfectly smooth, much less 

 narrow and quadrangular, and there is a difference of three and a half inches 

 in the length of the tail. It may be interesting to compare this serpent with 

 Herpetodryas aestivus and Dryophylax viridissimus, two slender green serpents, 

 the one from Surinam, the other from the United Slates. Herpetodryas astivus 

 and Chlorophis heterodermus are of nearly the same length, there being a differ- 

 ence of about 7 lines ; but the difference between the tails is greater, that of 

 iestivus being, in the specimen examined, 1 inch 81 lines longer ; but how marked 

 is the difference in the shape of the frontal plate ; the nostrils in Herpetodryas 

 open in a single plate, and although in both there are but one preocular and two 

 postoculars, they are altogether different in form ; in the one the eye rests upon 

 the fifth and sixth supra-labials, in the other (Herpetodryas) upon the fourth 

 and fifth. The arrangement and number of the temporal plates is difl'erent; in 

 Dryophylax, which is a much stouter and longer serpent, the frontal plate differs 

 from either of the others, the prefrontals pass down upon the side of the head 

 as far as the supra-labials, the pre- and postoculars, although the same in number, 

 still differ in shape, the position of the nostril is different, being between two 

 plates, the eye rests on the fourth and fifth supra-labial plates, and the size of 

 the eye differs, being smallest in Herpetodryas, largest in Chlorophis. If we 

 compare the supra-labials in the three we shall find them each of a peculiar 

 type ; in Dryophylax the sixth and seventh being remarkable for their large size. 

 The scales upon the body are also different. If we examine the teeth compara- 

 tively, we shall find that in Chlorophis the maxillaries, which are smooih, pre- 

 sent a marked curvature anteriorly, the points inclining backward, the three 

 posterior longer than the other, the two last more especially, which are also 

 much more robust ; neither of the posterior teeth appear to be grooved. In 

 Herpetodryas the teeth are smooth and resemble each other, (Aglyphodontes 

 isodontiens, D. and B.) In Dryophylax the posterior maxillary teeth are longer 

 and channelled, (Opistoglyphe dipsadien, D. and B.) Dryophylax is a South 

 American genus, exclusively, so far as is known, but Herpetodryas. according to 

 Dumeril and Bibron, exists not only in America, but in Madagascar and the 

 Isle of France. The following are the generic characters of Chlorophis : 



Maxillary teeth recurved, the posterior ones less than the anterior, the three 

 last larger than the others, the two hinder ones especially, which are not chan- 

 nelled ; nostrils between anterior nasal, and frenal; frenal remarkable for its 

 large size ; one antocular, two postoculars ; nine superior labials, the eye resting 

 on the 5th and 6th, and a very small part of the founh ; three anterior supra- 

 labials small, the three posterior large ; rostral rather high ; two internasals and 

 two prefrontals, vertical, pentagonal, much broader anteriorly, longer thau 

 broad, excavated laterally, presenting an acute angle behind ; occipitals pent- 

 agonal, well developed; supra-oculars not projecting; eyes round and quite 

 prominent; scales smooth, in 15 rows, quadrangular, about twice as long as 

 broad anteriorly, broader posteriorlv, the inferior row the largest ; a single pre- 



1857.] 



