CHAPTER XI. 



DEFINITION OF THE ORDER SAL1ENTU, LAURENTI, 1768. 

 (World-wide distribution.) 



Naked, tailless Amphibia of compact form, and with usually proccelous vertebrae. Cau- 

 dal vertebrae coalesced into a slender elongate piece, the urostyle. Two elements of the tar- 

 sus ossified and greatly elongated. Development by metamorphosis; gills never present 

 in adult. Ilium greatly elongated. 



The order is suggested in the Coal Measures by a single species, known from a 

 single poorly preserved specimen (plate 24, fig. I ) . The form Pelion lyelli Wyman was 

 the first known of the Linton Amphibia, and its striking frog-like (123, 639) appear- 

 ance was early noticed. There is no assurance that the species belongs with this order, 

 but since a well-developed and highly specialized frog (480, 481) occurs in the Como 

 Beds (405) of Wyoming, it is not impossible that we may have in the Pelion lyelli a 

 suggestion (460), at least, of the ancestral structure. It is certain that the frogs have, 

 in past ages, had a much greater length of vertebral column than they possess at pres- 

 ent, as is witnessed by the coalescence of several vertebras to form the urostyle. It 

 is suggested that the ancestral vertebral column is represented in Pelion. 



Family PELIONTIDJE Cope, 1875. 

 COPE, Bull. U. S. Nat. Mus., No. I, p. n, 1875. 



The present family includes but a single species, that of Pelion lyelli Wyman, 

 first described in 1858 (640), from Linton, Ohio. 



The family characters are to be found in the broad and obtusely rounded cra- 

 nium, in the frog-like scapular arch, the frog-like hind limb, and in the form of the 

 palate, so far as these structures have been preserved. 



It has been suggested that the present form shows decided affinities with the 

 frogs of to-day and it may possibly be looked upon as the actual ancestor of the liv- 

 ing frogs. The length of the vertebral column would seem to militate against such 

 a relationship, since it is well known that frogs have had a short vertebral column 

 since the Jurassic (480, 481). But this is not a good argument, since the developing 

 urostyles of modern tadpoles show metameric fenestrations in the developing bone 

 which doubtless correspond to openings between the vertebrae. The notochord of 

 the tail is segmented, apparently through the influence of former vertebral structure. 

 At any rate, the suggestion is an interesting one and, whether sustained or disproven, 

 the present discussion is based on the probabilities of the case. 



Genus PELION Wyman, 1868. 



WYMAN, Am. Jour. Sci. (2), xxv, p. 160, 1858 (Raniceps). 



COPE, Proc. Acad. Nat. Sci. Phil., 1868, 211 (Pelion, suggested in letter to Cope by Wyman). 



Type: Pelion lyelli Wyman. 



' ' The only specimen of the species exhibits an inferior view of a portion of the skeleton ; 

 and the obverse, on which the thoracic and abdominal armor could have been preserved, has 

 not come under my observation. The specimen, however, does not exhibit any ribs, although 

 the vertebras are well preserved. As observed by Professor Wyman, the genus pre- 

 sents some points of similarity to the Anura (Salientia). The prolongation of the angles of 

 the mandible is of this character, as well as the general form of the head. The bones of the 



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