288 R. L. Moodie — American Jurassic Frog. 



modern salientian ilium, with the anterior end greatly nan-owed 

 and pointed ; the pointed portion occupying one and one half 

 millimeters. The shaft of the ilium is flattened laterally. It 

 expands in width from a little less than one-half a millimeter 

 to slightly more than three millimeters. The articular surface 

 is marked by four pits which are the broken surfaces indicating 

 the firm union of the elements of the pelvic girdle. The 

 element is greatly thickened posteriorly, with a slightly devel- 

 oped, posterior, dorsal crest. 



The femur (No. 1862 Yale University Museum) is quite 

 distinctly amphibian of the salientian type. It is a slender 

 rod of bone from which the epiphyses have been lost, leaving 

 in their place pits occupying the ends of the bone ; indicating 

 the slight development of the endochondrium, as in all Am- 

 phibia. The lower end of the femur is divided into two sur- 

 faces by an imperfect partition, much as in modern frogs. The 

 upper end is peculiar in having a well-developed crest which, 

 in life, was undoubtedly capped by a large amount of cartilage. 

 In the fossil state it has been preserved as a spine. The femur 

 measures 12 mm in length, by 3 mra in distal width, by l mm in diam- 

 eter of shaft, by 2'5 mm in proximal width. 



The tibio-fibula (No. 1394 Yale University Museum) is repre- 

 sented by a portion of the lower end including 8 mi " of the ele- 

 ment. Its characters are so clearly those of the modern kSalien- 

 tia that a description is hardly necessary. The lower end is 

 divided by grooves, one on either side, indicating the previous 

 separation of the tibial and fibular elements, thus plainly show- 

 ing that the frogs have had a long pre-Jurassic history. 



The humerus of the other individual (No. 1863 The Yale 

 University Museum) is similar to the one described for the 

 type, though somewhat smaller. Like the type there is only 

 the lower half preserved, measuring but slightly more than l u,m . 



The Jurassic Frog thus indicated by these imperfect remains 

 was an animal about the size of Bufo debilis Girard of south- 

 western Kansas, and Texas ; though possibly shorter in its 

 bodily proportions as indicated by the short ilium. 



The above description will indicate, without a doubt, that the 

 Fobatrachus agilis of Marsh is the oldest Tcnownfrog. It is 

 hardly necessary to figure these imperfect remains since the 

 above description has been written with the skeletons of sev- 

 eral species of Salientia at hand and the comparisons are so 

 exact, the characters so identical and the frog skeleton has been 

 figured so many times that it hardly seems necessary. The 

 specimens are in Yale Museum, where they may be seen at any 

 time by anyone interested in a more direct generic and speci- 

 fic comparison. This has not been attempted in this short 

 account chiefly on account of the lack of skeletal material of 

 Fobatrachus agilis and on account of the lack of sufficient 

 recent skeletal material. 



