THE CLASSIFICATION OF THE OPHIDrA. 189 



apex or apices of the organ may be furnished with a rigid papilla (Fig. 5) or awn, or a 

 membranous disc. 



In the Tortricina and Peropoda (the constrictors) the hemipenis is not spinous and 

 the sulcus is bifurcate (Figs. 1, 2, 3), and in the Boidae the hemipenis is bifurcate 

 also, although in some genera (Xiphosoma, Ungualia) the branches are very short. 

 The external integument is never reticulate, but is always laminate with elongate 

 papilla? at the extremities, in Epicrates (Fig. 2), and Xiphosoma. The laminae are 

 pinnate from the sulcus as an axis in Morelia, Boa, Eunectes, Enygrus, Lichanura and 

 Eryx, and are transverse (flounced) in Charina (Fig. 3). In Uysia they are pinnate 

 (Fig. 1), with a few longitudinal plicae below. In the Colubroidea the majority of 

 genera are calyculate and spinous. Nevertheless, the Calamarinse are smooth or 

 papillose, and certain Tropical American forms are disciferous instead of calyculate. 

 Some are spinous to the tip. Among these, the Xatricinae have the spines minute, 

 but their weakness is offset by the presence of a few large hooks at the base of the 

 organ. The sulcus is either simple or bifurcate in the Colubroidea. 



Gradations in the characters of the hemipenis similar to those found in the Colu- 

 broidea are to be seen in the types of venomous snakes. Thus in the Proteroglypha 

 this organ is spinous to the tip, on a calyculate basis, in Hydrophis, Hydrus and 

 Elaps. It is reticulate at the extremities and spinous below in Dendraspis, Aden- 

 iophis (bivirgatus), Naja (Fig. 9), Acanthophis, Bungarus and Sepedon, the apex 

 with a smooth apex in the genus first named. 



In Solenoglypha, in the genus Atractaspis, the apex is calyculate plicate and the 

 remainder is spinous on a longitudinally laminate basis. In Causus the calyculate 

 structure is well developed. In the Viperidae and Crotalidse the spines are on a 

 flounced basis. The apices are calyculate in Bitis, Clotho (Fig. 10) and Yipera, and 

 spinous in Cerastes. They are calyculate in Crotalida? in Bothrops, Ancistrodon, 

 Crotalophorus and Crotalus (Fig. 11). 



The spines are not ossified in young snakes, and some may retain their flexible 

 condition to half-grown dimensions. The calyces are also tenuous and lacking in 

 papillae in young individuals. Hence it is important that adults be selected for exam- 

 ination. It is useless to expect to find the organs projected in any number of alcoholic 

 specimens ; and when projected, the terminal portion is not everted, but the spinous 

 portion only is exhibited. This part of the organ is apparently used sometimes for 

 defense. I have also found that females are two or three times as abundant in collec- 

 tions as males, a fact which would indicate that they are more easily captured. I have 

 failed, up to this writing, to secure males of a number of genera of which I have 

 access to females, which accounts for their omission from this paper. 



