704 REPORT OF NATIONAL MUSEUM, 1898. 



spiues are arranged in flounces. It is difficult as yet, and perhaps may 

 not become easy, to distinguish some members of the Lycodont group 

 from certain ground snakes with totally spinous hemipenis, especially 

 certain African genera, as Elapops, Grayia, and others. These ques- 

 tions remain for further research. 



I have found the characters of the hemipenis as constant as those of 

 any other part of the organism. Occasional irregularities are to be 

 looked for, but the onl^^ one which I have met with is in the case of a spe- 

 cimen of Boodoii infernal is from South Africa, in which the hemipenis is 

 shortly bifurcate on one side and not so on the other. There is a ten- 

 dency to bifurcation in some individuals of Opliiholiis getulus which is 

 not conspicuous in others, but this tendency does not appear in the 

 sulcus. It is a tendency only. While certain characters of this organ, 

 as already remarked, characterize series or groups of genera, others 

 characterize the genera themselves. These are given in the analytical 

 tables under the family and subfamily heads. On examining these 

 tables it will be seen that the genera brought into close juxtaposition 

 are frequently not most closely allied in general appearance. The leys 

 are only intended to present the penial characters; are not intended to dis- 

 play the serial or other relationships of the genera among themselves. 



1 now give the exact definitions of the divisions as far as definable 

 with present information. The definitions of the suborders are those 

 of Miiller, modified by myself.^ 



A. Paroccipital intercalated in tlie cranial walls {Angiostoma).' 



* No ectopterygoid ; palatines bounding choan;e posteriorly; ethmoturbinal 

 forming i)art of roof of mouth; rudiments of pelvis; two lungs. (Scole- 

 cophidia.) * 



I. Maxillary bone fixed to prefrontal and premaxillary ; a pubis Catodonta. 



II. Maxillary bone vertical and free from all others; no pubis Epanodoxta. 



** An ectopterygoid ; palatines not bounding choanje posteriorly. 



III. Maxillary bone free, horizontal Tortricina. 



B. Paroccipital attached scale-like to cranial wall and produced freely; ectoptery- 



goid present. (Eurystomata.) 



IV. Maxillary bone horizontal, not forming a ginglymus with prefrontal. 



COLUBROIDEA, 



V. Maxillary bone vertical and articulating with the prefrontal by a ginglymue; 



a tracheal lung Solenoglypha. 



In the following pages I present synoptical diagnoses of the genera 

 of the Serpentes arranged in key form. These are placed under sub- 



' Proc. Amer. Phil. Soc, 1886, p. 479. 



2 This arrangement was first published by the writer in the Proceedings of the 

 Academy of Natural Sciences, Philadelphia, for 1864, p. 230. The definitions of the 

 lower primary divisions were derived from J. Miiller. It was published in greater 

 detail, with the characters of all the families in the Proceedings of the American 

 Philosophical Society, 1866, 479, and in the Bulletin of the U. S. National Museum, 

 No. 32, 1887, p. 47. 



3 The characters of this division as I originally gave them (Proc. Acad. Nat. Sci. 

 Phila., 1864, p. 230) were derived from J. Miiller, which have been shown to b© 

 partially erroneous by Dumeril and Bibron, and Peters. 



