I 



THE BATRACHIA OF NORTH AMERICA. 253 



XENOriDJE. 



No ribs; vertebrae opisthocoelous ; os ilinin attached to the ninth 

 A^ertebra only. Coracoids and epicoracoids well separated from those of 

 the opposite side. Teeth present j sacral diapophyses dilated. 



One genus, Xeuopus, with three species in the regio ^thiopica. In 

 this the iiiterorbital ethmoid plate, though long, is not produced ante- 

 riorly, and is entirely' concealed by the frontoparietal. Fronto])arietal 

 strongly ossified, overhanging the con fluent prefrontals. The i^refroutal 

 does not always extend to it. The first two vertebrai are separate, but 

 the sacral and coccyx confluent. There are ossa nasalia above the 

 nares. Terminal phalanges acute, simple. External metatarsals sep- 

 arated by a web, (Plates 49, fig. 10 and 69, fig. 2.) 



PAL^OBATRACHID.E. 



No ribs ; os ilium attached to the diapophyses of the confluent ninth, 

 eighth, and seventh vertebriie, which form a disk; urostyle attached by 

 a double glenoid cavit3^ Frontopaiietal strongly ossified, not produced 

 farther than the separate prefrontals. External metatarsals probably 

 separated by a web. 



The genus PakeohatracJins, Tsch., represented by several species in 

 the Miocene of Germany. The superior plate of the ethmoid was con- 

 cealed, and the atlas contiuent with the first vertebra, leaving but six 

 between the occiput and sacrum.* 



Von Meyer describes the vertebra; of P. giganteus as procoelous, while 

 some of them are figured as opisthocoelous. Woltersdorftt states that 

 they are procoelous, A S])ecimen in the British Museum which I 

 examined has opisthocoelous vertebrae. It remains, therefore, a question 

 of interest whether this family belongs in the Aglossa. Woltersdortf, 

 who has studied it very carefully, refers it to the Arcifera, and to the 

 neighborhood of the Pelodytidse, although admitting various points of 

 resemblance to Xenopus. He describes nine species from various parts 

 of central Europe. 



AECIEEEA. 



In this tribe the extremes of the series are more diverse than in the 

 others, and depend on the following features : 



(1) In that nearest the Aglossa the vertebrte are, like those of the 

 latter and of the Salamanders, concave posteriorly and convex ante- 

 riorly ; in the other extreme the reverse. These features are not as ir- 

 reconcilable as might at first sight appear, as the intervertebral spheres 

 do not become firmly attached to either centrum at maturity in some 

 individuals of Borhoroccvtes ijeronii^ Pelobates fuscus (Stannius), and 

 Cultripes provincialis (Duges). (2) Those with opisthocoelous vertebra) 



*" Palseontographica, in, p. 147. 



t Ueber fossile Fro&che msbes. das g. Palseobatraclius, Magdeburg, 1886. 



