NO. 1696. AIR-BREATHING VERTEBRATES— HOODIE. l^ 



even flaked off portions of the soft coal on which the animal is em- 

 bedded, without detecting at any point the slightest trace of an ab- 

 dominal armature. The absence of scutellse is complete, since there 

 is no reason why they should not have been preserved, as the skeletal 

 elements are in place and undisturbed by any post-mortem shifting. 



The relationships of this peculiar reptile are not known. Its close 

 affinities with the Microsanria is firmly established by many struc- 

 tural resemblances, but to what group of reptiles it may be related is 

 uncertain. There are but few characters preserved on which a rela- 

 tionship could be established. The two sacral vertebrae, the phalan- 

 geal formula, and the ossified carpus and tarsus are the only true 

 reptilian characters present in the specimen. Too much stress has 

 been laid on the phalangeal formula as a basis for relationship, and 

 a study of the Microsauria has shown that the presence or absence of 

 ventral armature is of no particular importance, as has been shown 

 to be the case with epiphyses, on which two groups of reptiles have 

 been related. No member of the- genus Tuditanus possesses abdom- 

 inal ribs or scutellse, but in closely related forms, like Saurerpeton, 

 SaurojjJeura^ and Ctenerpeton^ the abdominal ribs or scuta? are pres- 

 ent in great profusion and with well-marked characters, which have 

 been taken as generic landmarks. 



The morphology of the ventral armature still remains in mystery. 

 Its origin is not to be explained on the basis of the structures found 

 in any Carboniferous air-breathing vertebrate. The earliest branchi- 

 osaurians possess ventral scutes, and the earliest microsaurians pos- 

 sess them. Their origin and function are to be explained with the 

 solution of the problem of the origin of the Amphibia from their 

 piscian ancestor, which has not yet been discovered. 



Measurements of Isodectes piinctnJahis Cope. 



mm. 



Length of entire specimen, as preserved lo2 



AVidtli across body, in middle of dorsal region IS 



Length of digit I of the hand i 11 



Width of nlnare 2 



Length of metacarpal, second digit 4 



Length of rib in dorsal region 9 



Width of same rib . 7.5 



Length of dorsal vertebra 4 



Width of same 3 



Length of presacral region preserved 00 



Length of sacral region 8 



Length of ilium 9 



Greatest width of the ilium 3 



Length of femur 15 



Pi'oximal width of the femur 5 



Median width of femur 2 



Distal width of femur 4 



Length of tibia ' 8 



