58 PEOF. G. B. HOWES AND ME. H. II. SWINNEETON ON THE 



The Mandible. The mandibular ramus has been shown by Baur to consist (95 a . 

 p. 413) of the six elements usually present in that of other Reptilia. He originally 

 described it in 1891 1 as resembling most closely that of those Chelonia in which the 

 angular and supra-angular, apposed behind the splenial, under-arch the articular, and 

 as destitute of the 7th element or " praesplenial " described by him in these animals. 

 We have only to add that at the latest stage observed by us (T) the articular has not 

 yet appeared, the articular region being still cartilaginous, and that at Stage S the 

 angular and supra-angular (s.a., PI. IV. fig. 4) are still separated by the splenial (sp.). 



6. THE APPENDICULAR SKELETON. 



The Pectoral Girdle. Concerning this we have little to record. The simplicity of 

 the coracoid was pointed out by Giinther, in the remark (67. p. 611) that it has 

 " no notch whatever." Furbringer, in a passing allusion seven years later 2 , commented 

 on the rounded border and feebly ossified state of this (PI. VI. fig. 6, cor.), and there 

 can be no doubt that in respect to these features it simplifies the Lacertilian type. As 

 pointed out by Furbringer, however, the Chameleons approximate to a similar con- 

 dition, but it may be questioned whether the " simplification " in them is not due to 

 secondary causes. Ossification takes place during Stages S and T, on lines common to 

 both the Batrachia and Reptilia. An interesting detail is the early appearance of the 

 clavicle, viz. at Stage Q (PI. VI. fig. 4, cl.), at which no cartilage-bones are anywhere 

 present in the axial skeleton. The interclavicle appears later. We have failed in all 

 attempts to find evidence of a cartilaginous predecessor of these bones. 



The relationships to the sternum we have already described (antea, p. 33). 



The Pelvic Girdle. Giinther accurately described the adult girdle, except that he 

 applies to the ileo-pectineal process the term "uncinate" (67. p. 615). Like the 

 shoulder-girdle, it is at Stage Q fully chondrified. Its two halves (PI. VI. fig. 7) are 

 united, and there is a considerable cartilaginous symphysis (c.i.p.) which in the mid- 

 ventral line separates the cordiform fenestree (f.c.). With later growth (at Stage R) 

 a backwardly-directed median process (the hypoischium of Mehnert 3 ) becomes con- 

 spicuous, but it is never segmented off or ossified to form an " os cloaca?" as in 

 Lacerta. The epipubic cartilage (e.) like it is simple i. e., there is nothing to 

 suggest those processes of bifurcation and subdivision recorded for certain Lacertilia. 



Interest attaches to the ligamentum medianum pelvis, from the fact that while 

 Wiedersheim has described 4 in its place in the adult a cartilaginous tract uninter- 



1 In his 1895 notes he admits a transposition in those of 1891 of the terms angular and splenial, but it 

 does not affect his comparison. 



2 Furbringer, M. : Morph. Jahrb. Bd. i. 1876, p. 643. 



3 Mehnert, E. : Morph. Jahrb. Bd. xvii. 1891, p. 123. 



4 Wiedersheim, E. : Zeitschr. wiss. Zool. Bd. liii. 1892, p. 54. 



