ON DEGENERATE TYPES OF SCAPULAR AND 

 PELVIC ARCHES IN THE LACERTILIA. 



E. D. COPE.i 



Paleontology has rendered it possible to assert that the rudi- 

 mental condition and absence of limbs observed in many genera 

 of Lacertilia are a result of retrogressive evolution or degen- 

 eracy.2 These degenerate conditions are seen in genera of the 

 superfamilies Diploglossa, Leptoglossa, Annielloidea, and Am- 

 phisbsenia. In the remaining six superfamihes such conditions 

 have not been observed, except in such cases as Sitana (Agami- 

 dce), where a single digit is absent from the posterior foot. 

 Certain questions respecting the origin of the degenerate forms 

 naturally arise. One of these is, Is the manner of degeneracy 

 in each superfamily or family characteristic of it, and different 

 from that obtaining in other families ? Secondly, What is the 

 order of degeneracy ? what parts disappear first and which are 

 longest persistent.? Thirdly, Can any relation between the 

 manner of degeneracy and the life history of the genus be 

 traced ? The following investigation was undertaken with the 

 object of throwing light, if possible, on these points. The 

 material at my disposal has not been sufficient to enable 

 me to answer any of these questions in a final way, but some 

 information has been gained which will aid in future research. 

 Fifteen species have been examined, six of which belong to the 

 Diploglossa, five to the Leptoglossa, one to the Annielloidea, 

 and three to the Amphisbaenoidea. All of the families known 

 to possess degenerate types are represented, excepting the 

 Gerrhosauridse and the Dibamidae, of which the former has but 

 five genera, two of which are degenerate, and the latter but one 

 genus. Thus a general view of the subject has been obtained. 

 Of these species eight are described for the first time; viz. 

 two Diploglossa, four Leptoglossa, one Annielloidea, and two 



1 Read before the U. S. National Academy of Sciences, November lo, 1891. 



2 Origin of the Fittest, 1887, p. 337. 



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