1896.] NATURAL SCIENCES OF PHILADELPHIA. 465 



coarsely plicate transversely, the plicae extending to the welt. On 

 the other side, the transverse plicae terminate at a band of fine lon- 

 gitudinal folds. In Ophisaurus the organ is undivided, and there 

 is a welt with one edge and the proximal end free. It is covered 

 with robust papillae. 



In Xantusiidae the hemipenis is bifurcate and is shortened as in 

 many Gecconidae, appropriately to the fragile tail. There is a welt 

 on each side of the sulcus spermaticus which follows a short spiral 

 direction. Opposite to the sulcus are two short, thick welts, which 

 have the direction of parts of consecutive threads of a screw. All 

 of the welts are deeply cross-folded. 



In the Tiid?e two types may be observed of the structure of the 

 hemipenis, but I have not had access to sufficient materia! to enable 

 me to refer all the genera to the one or the other. In the typical 

 members, as in the genera Dracaena, Tupmavibis, Amiva and Cne- 

 midophorus, the pattern consists of numerous delicate, imbricate, 

 transverse laminae which are closely applied to each other. Oppo- 

 site the sulcus all the genera display a welt, which has free borders. 

 These are entire in Dracaena and pectinate in Amiva and Cnemido- 

 phorus ; between these and the borders of the sulcus is a rounded 

 welt on each side. The laraince are sublongitudinal, diverging prox- 

 imad from the sulcus ; on the first welt they turn sharply distad ; 

 between this and the welt they make a second chevron distad, turn- 

 ing proximad. Proximad of the median welt these lamina meet, 

 forming a curve or chevron turned proximad. In Oiemidophorus 

 there is one less chevron. In this genus and Amiva there is a 

 strong, fleshy papilla at the apex of each tract between the welt and 

 sulcus. 



A modification is seen in Centropyx (pelviceps). Here there is a 

 narrow welt opposite the sulcus ; on each side of the sulcus a prom- 

 inent welt diverges from it proximad and approaches the proximal 

 end of the median welt, so as to enclose a space with it. It is trans- 

 versely plicate and the enclosed space on each side the median welt 

 has the delicate transverse lamination characteristic of the Tiidse. 

 What is entirely peculiar is. the presence at the apex of each of the 

 laminate spaces of a large patch of acute flexible papillse. 



The plan is the same in Anadia bogotensis, but the details are dif- 

 ferent. The organ is bifurcate. A strong welt opposite the sulcus 

 is divided into fine longitudinal folds, which are crimped trans- 

 versely. The space between this and the sulcus is marked with 



