NATURAL SCIENCES OF PHILADELPHIA. 167 



Muzzle produced beyond the labial margin, oblique-truncate in profile. Ros- 

 tral plate flat, not turned backward above. Both pre- and postfrontals longer 

 than wide, the latter a little bent dowu laterally. Vertical more than twice 

 as long as wide, lateral outlines not straight. Superciliaries broad ; occipitals 

 rather short, longer than broad ; two postoculars, in contact with one tem- 

 poral. Oue preocular just touching vertical ; one longitudinal loreal, higher 

 behind ; one elongate nasal, the nostril anterior to its middle and connected 

 by a suture to the margin below Superior labials eight, third, fourth and 

 fifth entering orbit ; inferior ten ; post- longer than pregeneials. Anterior 

 maxillary and mandibular teeth longer than median. Pupil round. Scales 

 broad, thin, poreless, in nineteen rows. Tail rather slender. Gastrosteges 186 ; 

 one divided anal ; urosteges 67. End of muzzle to rictus oris 7 lines, to vent 

 6 in. 2 1. ; tail 4 in. 5 1. 



General color light brown, punctulate with dark brown, especially thickly 

 on head and sides. A darker brown band three and two half scales wide 

 from occiput to end of tail, which is nearly broken into spots on the nape. 

 Ends of scuta and first two rows of scales darker, especially auteriorly, where 

 the band is sooty and spreads over the lips and chin ; a faint longitudinal 

 band above the shade ; a short yellow streak from postorbitals to penultimate 

 labial. Abdomen with many short punctulate streaks. 



Hub. Colima, Mexico. Xantus coll. No. 1341. Besides the preceding, this 

 very fine collection contained Spilotes auribund us (=salvini Gthr.), S. 

 erebennus (obsolelus Holbr.) Conophis lineatus, Phimothyra mexi- 

 c a n a (Zamenis D. &. B.) and the following : 



Toluca frontalis. 



Muzzle prominent, acuminate, slightly recurved. Rostral separating pre- 

 frontals very slightly. Nasal long ; postfrontal in contact with second supe- 

 rior labial. One narrow low preocular, two postoculars, the lower barely in 

 contact with one temporal. Seven superior labials ; eye over third and fourth. 

 Occipitals longer than vertical, truncate, rounded behind ; anterior suture of 

 vertical a little longer than straight lateral. Seventeen rows of equal thin 

 scales. Seven inferior labials ; geneials very short, posterior pair reduced 

 to scales. Urosteges 44 ; one double anal ; gastrosteges 141. End of muzzle 

 to canthus oris 8 lin. ; to vent 8 in. 10 lin. Length of tail 1 in. 10 lines. 



Color below uniform pale yellow. Above grayish brown, becoming more 

 rufous medially, with about thirty- six rhombic, dark edged, brown spots, six 

 scales wide and four long, whose angles are produced as vertical lateral bars. 

 Together they become nearly cross-bands posteriorly, when they are sepa- 

 rated by a pale spot on the vertebral line. A brown cross-band across post- 

 frontals and vertical ; a longitudinal band on each occipital and side of nape. 



Bab. Colima. Xantus coll., No. 1363. 



In this genus and Tomodon the hypapophyses of the vertebras are, a? usual 

 among the Asinea, not developed behind the anterior fifth or sixth of the 

 column. A group of genera partly coinciding with that forming Jan's family 

 Potamophilida;, I find to possess these processes even to the vent, offering a 

 new character of definition to the subfamily of the Homalopsinae, as tbey 

 may be called. The genera in which this structure exists are Eurostus D. and 

 B., Gerarda Gr., Hypsirhina Wagl., Cerberus Cuv., Homalopsis Kuhl., Heli- 

 cops Wagl., Atretium Cope,' Tachynectes Fitz., (this genus is coryphodont in 

 dentition ;T. chrysostictus is a Helicops) ; Trop'idonotus Kuhl., Tham- 

 nophis Fitz., Xenochrophis Gthr., ( = Thamnosopkis Jan), Prymnomiodon 

 Cope, Ninia B. and G., Storeria B. and G., Haldea B. and G., Tropidoclonium 

 Cope, Amastridium Cope. In Herpeton the processes are present, but very 

 weak for a short distance posteriorly. In Tretanorhinus, otherwise similar 

 to this group, there are only strong keels, as in a few Colubrine genera. Gla- 

 niolestes and Heterodon do not belong here ; the processes are wanting ; so 

 also with Xenodon and Thamnodynastes. Hydrops and Calopisma belong to 

 another section. 



1864.] 



