30 



coracoid has the same form as that of Sphenodon. And, moreover, 

 it follows from the above description of the development of the 

 coracoid of the lizard, that the incitsura scapiiio-coracoidea has the 

 same genesis as the dorsal fenestra of {Jiiemidophorns, save that 

 in Lacerta the cranial border also is practicall}' enlirelj reduced 

 (except for the remains of cartilage). Thus also the coracoideum of 

 Lacei'ta with one fenestra contains, altliougii it seems somewhat 

 paradoxial, a second, dorsal fenestra. Conse(|iiently tlie so-called 

 procoracoid of the lizard is the sum of what is in multiple fenestrated 

 coracoidea termed the procoracoid and mesocoracoid (mesocoracoid 

 lies between fenestra principalis and dorsal "Nebenfenster"). By the 

 pi'Ocoracoid in the order of Sauria are thus nnderslood different 

 |iarls of the girdle. 



This fact, as well as the development of the coracoid (taken in 

 a wider sense), induce me to side with Gotte; the whole ventral 

 portion of the piiinary shoidiler-gii'dle of the Saiiiia, with or without 

 fenestrae, corresponds merely to the coracoidenm of the Urodela 

 and Annra. Respecting the latter Gotte has already demonstrated 

 that their shoulder-girdle (with one fenestra) does not acquire its 

 definite form tiy fenestration, but that it passes through an Urodelan 

 stage (Raiia esculenta). The fact that the adult shoulder-girdle of Lacerta 

 corresponds to that of e.g. Rana thus depends upon caeno-genesis. 

 The diflfei'ent parts of the two shoidder-girdles are not homologous. 



The crocodilia, in which a procoracoid is lacking, will thus, like 

 Sphenodon and Chamaeleo, possess a coracoid homologous with the 

 whole pars coracoidea of the primary girdle of Lacerta. In short, 

 as far as our knowledge extends at present (regarding Chelonia 

 there are no genetic data) we are not obliged in the case of any 

 reptile to assume a procoracoid that is homologous with Ihe pro- 

 coracoid of the Amphibia. 



Gkgenbauer postulated the homology of the episternum of the 

 reptiles and mammals; the difference in the histological structure 

 (reptilia : bone; mammals : cartilage or bone), and in tlie histogeny 

 reptilia : desmal, and in mammals chondral ossification) was evidently 

 no objection, although he did consider as an objectioji (he fact that 

 the episternum of the Sauria lies venfi'al and that of the mammalia 

 cranial from the sternum. Anotiier weak point in the theory of this 

 homology is that the episternum of the mammals is generally held 

 to be a clavicular sternum, i.e. that we see in this episternum a 

 product of the claviculae, whereas most of the researchers who 

 studied the episternum of the Reptilia did not succeed in establishing 

 a genetic connection between the clavicle and episternum. 



