204 REPORT OP NATIONAL MUSEUM, 1898. 



Comparison of Diploglossa. — The degeneracy in this series is tolerably 

 consistent in the order of its progress. In none of the genera are fore 

 limbs present, and in three of them hind limbs are present. Notwith- 

 standing the universal absence of fore limbs, a scapular arch is always 

 present. This region shows, however, successive stages of degeneracy, 

 as follows: In the three genera without posterior limbs the sternum 

 has costal articulations; in the other three, none. In the genera with 

 costal articulations the number of the latter diminishes regularly: in 

 Mancus, three; in Opheodes, two; in Pygopus, one. Of the three genera 

 with costal articulations, the iuterclavicle is present in two; in one 

 {Pygopus) it is wanting. In the other genera it is present in a much 

 modified form and position in one genus {OpMsaurus). Clavicles and 

 coracoids are osseous in all of them; but the procoracoid is osseous in 

 only two genera ( Opheodes and Pygopus) ; while in the third genus with 

 costal articulations {Mancus) it is cartilaginous, as in the genera with- 

 out costals. The genera with costal articulations are also the only ones 

 with osseous scai^ula. So we observe a certain order in the loss of 

 parts. Thus, the part to disappear first is the iuterclavicle (to reaj^pear 

 in OpMsaurns) ; second, costal articulations and osseous scapula; third, 

 sternum, which diminishes in size until greatly reduced, as in Anguis 

 and Dopasia. 



As regards the i)elvic arch, reduction of its elements precedes the loss 

 of limbs. Thus, Mancus is the only genus where the pubis and ischium 

 meet (or in the ischium, are connected by an osseous hypogastroid) on 

 the middle line. In Opheodes, where the posterior limbs are much 

 as in Mancus, these elements are separated below the pubes widely. 

 In Pygopus, where the limbs are better developed than in either, the 

 inferior pelvic elements are rudimental and widely separated, being 

 merely processes of the ilium. In the genera without limbs ( OpMsau- 

 rus with a minute rudiment) this reduction is carried still farther, the 

 inferior elements not being distinguished from each other or from the 

 ilium, the entire arch having a lateral ijosition. Miiller remarks of 

 these parts in Pseudopus, OpMsaurus, and Anguis, that they are "zwar 

 sehr iihnlich." The order of degeneracy, then, in the pelvic append- 

 ages in the Diploglossa, is, first, reduction of inferior j)ieces; second, 

 loss of limbs; third, fusion of all the elements into a single lateral bone. 



Comparison of the Leptoglossa. — In Chalcides we have nearly normal 

 scapular and i)elvic arches, while the limbs are very much reduced, 

 though not to be termed rudimental. In the next stage of reduction, 

 where all the limbs are present, but rudimental, the two arches show a 

 considerable degradation, which is more marked in the scapular than 

 in the pelvic. The pelvic elements remain much as in Chalcides, but 

 reduced in size merely. In the scapular arch the sternum loses two 

 costals, and the iuterclavicle loses the transverse processes. The clavi- 

 cles become simple, and the ossification of the scapula and coracoid is 

 reduced in extent. In Propus, where the fore limbs are much as in 



