NATURAL SCIENCES OP PHILADELPHIA. 299 



pi urn* and T. anoscopus;f i.e. the approximation of the external nares 

 and consequent restriction of the prefrontal plates and the narrowing of the 

 superciliary plates, to give that vertical position of nostrils and range of vision 

 so characteristic of the most highly aquatic types of serpents. The union of the 

 prefrontal plates as in Dimades plicatilis is but one step further. Be- 

 tween the latter species and Trop. r h o m b i f e r, the Tretanorhinus may be 

 said to be exactly intermediate in respect to position of nares and eye, carina- 

 tion and number of scales, and coloration. Besides this passage from the Tro- 

 pidonotinae to the Homalopsinte, there is some analogy or affinity between 

 such species as Tropidonotus d i m i d i a t u s and g r a h a mi i and Hypsirhina 

 en hydris of the Old World. A similar connection may be traced through 

 AtretiumJ schistosum. 



Thamnophis cyrtopsis Cope. Eutaenia cyrtop&is Kenn. Proc. A. N. S. Phil. 

 I860, p. 333. 



Var. c y c 1 i d e s Cope. 



A single specimen from Cape St. Lucas, Mr. Xantus' coll. (Smiths. No. 5023,) 

 corresponds in most respects with Mr. Kennicott's description, but differs as 

 follows : The first dorsal row of scales is smooth; th j re are no spots upon the 

 extremities of the gastrosteges ; the seventh upper labial shield is principally 

 bordered with black on its posterior border ; there are two rows of small alter- 

 nating black spots posterior to the post-occipital pair, instead of a single row 

 of large ones; on the anterior third of the body there are two rows of small 

 alternating spots, the inferior in contact with the lateral stripe, covering one or 

 two scales, the superior in contact with the vertebral, and soon disappearing. 

 The inferior series is larger near the middle of the body, but is lost posteriorly. 

 The skin is marked with the usual large spots, forming a zigzag series. The 

 head is very broad posteriorly, the muzzle short, the frontal region very de- 

 clive. 



* This species has been sent from Florida by Mr. Wiirdemann to the Smithsonian 

 Inst. Specimens obtained in Souihern Illinois by Mr. Kennicott probably belong to the 

 same. 



t Tropidonotus anoscopus Cope. Scales small, in twenty-three rows, all 

 keeled except those of the first, which are of small size. Scale pores in pairs. Dentition 

 syncranterian. Head oval, muzzle short, obtuse, profile plane. Rostral plate twice as 

 broad as high, its labial bordf r much shorter than the nasal. Nasal plates but little 

 separated anteriorly by the prefrontals, scarcely touching the postfrontals ; nostrils sub- 

 vertical. Loreal higher than long. Preocular narrow, not in contact with the ver- 

 tical. Prefrontals very small, subtriangular ; superciliaries narrow; vertical elongate 

 with parallel lateral borders; occipitals rounded posteriorly, bounded by one large and 

 six smaller temporals. Postoculars two, the inferior and half the superior in contact with 

 one temporal, also a series of small scales which separate the orbit from the superior 

 labial plates. The latter are nine in number, the seventh largest, fifth beneath the mid- 

 dle of orbit. Syinphyseal very small, transverse, ten inferior labials ; genials elongate. 

 Gastrosteges 143, one divided anal, urosteges 73; toial length 14 in., of tail 3 in. 6 lin. 

 General color above, dark plumbeous brown, with blackish vertical bars, alternate upon 

 each side, one, or one and a half scales wide, and three and a half or four scales apart. 

 Beneath dirty brownish white, each scutum brown at the base. Head and jaws brown. 



Habitat. Cuba. Mus. Acad. Nat. Sciences. 



This is probably the Tropidonotus cy clopio n with 23 rows of scales of the Erpeto- 

 logie Generale. Compared with Floridan specimens, noted above as the true c y c 1 o- 

 p ium, ivith 29 or 31 rows of scales, we observe the following peculiarities in the latter, 

 which are not shared by the former. The rostral plate is as high as broad ; the nasals 

 largely in contact with the postfrontals; the loreal triangular, lunger than high; the pre- 

 ocular divided ; two large and one small temporal bounding each occipital ; eight superior 

 labials, twelve inferior. Seven superior labials are assigned to the cyclopionin the 

 Erpetologie Gen. In T. r h o m b i f e r, the aspect of the nares and orbits is less ver- 

 tical, the rostral plate is as high as broad, and the dorsal scales and labials are different in 

 numbers and proportions from those of the anoscopus. 



X Atretium Cope, Tropidophis Gray, 1849, not Bibron, 1843. 



1861.] 



