PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. 65. 



SappeH: Loreal present, ventrals 153-158, maxillary teeth 14, 

 16-2, a groove visible under magnification of 80 diameters. 



The hemipenis, hypapophyses, coloration, and habit of the two 

 species are identical. Both have 17 rows of smooth, pitless, scales. 

 Both have "oculars 1-2, temporals 1-2; a divided anal, a single nasal, 

 and the third and fourth upper labials entering the eye. The fol- 

 lowing list will indicate the further scalation and the provenance of 

 the specimens : 



Source. 



Labials. 



Locality. 



Cope, 1866 



Boettger, 1898 



MuS. Comp. Zool., 15319 

 U. S. Nat. Mus., 29216.. 

 U. S. Nat. Mus., 29217.. 



Werner, 1903 



U. S.Nat. Mus., 46509.. 



7/9 Cocuyas, Panama. 



7/ San Jose, Costa Rica. 



7/9 I Cariblanco, Costa Rica. 



7/8-9 ! Greytown, Nicaragua. 



7/8 I Uo. 



7/ Guatemala. 



7/9 j Chicharros, Mexico. 



In the Museum of Comparative Zoology No. 15319 the parietal 

 meets the fifth labial on each side. Cope (1866) described his speci- 

 men (a male) as with keeled scales in the anal region. This is the 

 case in the two large males I have seen in the United States National 

 Museum (Cat. No. 29216 and Cat. No. 46509), but not in a very 

 small male (Cat. No. 29217) nor in either of the females. Boettger 

 and Werner do not mention this peculiarity. 



The color is black, with a white dot on about every fourth scale 

 of row 5. The upper surface of the head is light. 



The hemipenis has two very large hooks which occupy the basal 

 third, then increasingly smaller and more numerous hooks passing 

 gradually into calyces which occupy the distal fifth. The sulcus 

 is divided for the distal third. 



The relationships of this genus are somewhat to seek. Perhaps 

 examination of various characters in order will set forth more clearly 

 the diverse genera allied. 



Hemipenis : Among the snakes whose hemipenes are known Thatn- 

 nodynastes possesses male organs almost exactly like those of Anias- 

 tridium. Tretanorhinus and Hydrocalamus each have four large 

 basal hooks instead of two, and in each the calyculate area has a free 

 proximal edge — that is, is " capitate." Diadophis has numerous 

 basal hooks. 



Dentition: The dentition of Thamnodynastes, of Paraoxyrhopus 

 and of Hydrocalamus is the same as that of AtnaMridum. That of 

 Diadophis differs in the absence of a gap in the tooth row anterior 

 to the two enlarged teeth. Many other forms have closely similar 

 dentition. 



