EXTINCT BATRACHIA. 371 



throughout; the laminar expansion is quite thin; while the distal end 

 is expanded and concave, perhaps for the attachment of cartilage, al- 

 though no trace of this remains on the shale. The neural spines have 

 short bases, oblique anterior and nearly straight posterior borders, with 

 obtuse extremity. I perceive no essential difference in the smaller spe- 

 cimen, which is one-third less than the types. 



The limb is appropriate in its proportions to the present species, and 

 may be described in this place. The first segment is one-third longer 

 than the second, and has a transversely expanded head. The shaft is 

 stout, the distal extremity not expanded and concave. The second seg- 

 ment is stout, more expanded proximately than distally, the proximal 

 end truncate and slightly concave. A bone, much displaced, lies near 

 it, and is probably ulna or fibula ; it is as stout as the first, the end 

 not expanded. Of metatarsals there are two, three-fifths the length of 

 the second bone of the leg, and of phalanges two, of two digits each. 

 The proximal are three-fourths the length of the metatarsals, and indi- 

 cate elongate toes. The obverse of this specimen is preserved, and con- 

 tains no additional toes or phalanges. 



Length of a vertebral centrum, .014 m.; depth of a vertebral centrum, 

 .009; depth of entire vertebra, .022; length of neural spine, .008; 

 height of neural spine, .006 ; length of a rib on curve, .042 ; width of a 

 rib at ala, .009; width of a rib at extremity, .005; length of first seg- 

 ment of leg, .038 ; length of second segment of leg, .024 ; length of meta- 

 podial bone, .010; length of first phalanx, .007. 



Ceraterpeton, Huxley. 



The single example on which the American species of this genus is 

 established is a dorsal view of the posterior part of the cranium, and 

 the anterior part of the vertebral column. From this we learn that the 

 genus is characterized by the possession of osseous vertebrae ,with ribs, 

 stout fore limbs, thoracic shields, and a cranium with sculptured surface. 

 It also presents a remarkable development of the epiotic bone into a 

 horn directed backwards, resembling in general that of Ceraterpeton Gal- 

 vanii, Huxl. The number of digits can not be determined, nor is the 

 existence of abdominal scuta or rods ascertainable. The ribs are not 

 alate. 



As compared with Ceraterpeton Galvanii, Huxl., this form presents no 

 material difference ; the absence of the abdominal scutella may be due 

 to the dorsal view presented by the specimen, and be only apparent ; in 

 C. Gqlvanii they are quite minute. 



