CROCODILIANS, LIZARDS, AND SNAKES. 683 



tvrenty-three other species inhabit Africa, with the exception of the 

 three species of the genera Blanus, which belong to the Mediterranean 

 district. 



SYNOPSIS OF THE GENERA. 



A. Segments of the pectoral region not differentiated. 



1. The nasal plates lateral, separated from each other on the median line. 



rt. Nasals separated by the rostral. 



Rostral with a median cutting edge, extending between the fronto- 

 nasals Anops Bell. 



Rostral flat, not extending between frontonasals Diphalus Cope. 



aa. Nasals separated by the frontonasals. 



Frontonasals united into one plate; no frontals Blanus Wagler. 



Frontonasals united ; frontals present . .- Cadea Gray. 



2, The nasal plates in contact with each other on the median line. 



a. Preanal pores present. 



Nasal plates distinct Amphishwna Linntcus. 



"Nasal plates united," Gray Typhloblanns Fitzinger. 



Nasals, frontonasals, and anterior labials united. . OpMoproctes Boulenger. 

 AA. Segments of the pectoral region more or less enlarged, or forming angular 

 series. 



Snout compressed Geocalamus Giinther. 



Snout depressed ; nostril in a small, separate nasal ; tail cylindical. 



Monopeltis Smith. 



Tail depressed, above with rows of round tubercles Bhineiira Cope. 



Nostril pierced in the rostral Lepidosternon Wagler. 



Anatomy. — The characters of the regions of the arches and limbs have 

 the following characters in Amphishcvna occidentalis Cope: 



No scapular arch nor limbs ; a rudimental pelvic arch. 



Felvic arch. — This consists, in this species, of a slender bone in the 

 abdominal wall, a little in front of the vent on each side, which is 

 directed forward and inward, but without meefing its mate on the 

 middle line. It has no articular connection with any other element. 

 In AvipJdsbcena alba this element is similar, but is relatively shorter 

 and more as figured by Fiirbringer in the A.fuliginosa. This species 

 has also, according to Fiirbringer, a very rudimental scapula. 



As the left lung only is present in this family, there is but one gas- 

 tropulmonary mesentery. The liver has a cresceutic cross section, and 

 it is sup])orted by two gastrohei)atic mesenteries {Anq)hisba'na alba 

 and A./Hliginofia), or by only one, and a right hepatic, or hepatolateral, 

 as it may be {Rhineura floridana). There is but one hepatoventral. 



The onlj" species of which I have obtained a satisfactory hemipenis is 

 the African Moiwpeltis galeatus Ilallowell. The organ is bifurcate ; each 

 branch is marked with fine, close, transverse folds, while the region 

 proximad of these has coarser folds directed transversely and obliquely. 



Origin. — No information as to the origin of the Amphisba^nidie or ot 

 the Annulati was accessible until Dr. Baur in 1893 ^ announced the 

 discovery of two species in the Oligocene beds of South Dakota, where 



1 American Naturalist, 1893, p. 998. 



