REPTILES. 91 



muscles, some of which were attached to them, whilst others only covered their outer surface. Of the 

 muscles that were attached to them there were four pairs. The first pair originated from the two ends 

 of a strong occipital ridge, passing from thence obliquely downwards and backwards, presented 

 a moderate thickness, expanded considerably in a fan-like form, and corresponded in their origin 

 and direction to the sterno-cleido-mastoids of other Saurians. Still, only a few of their fibres 

 were attached to the bony pieces in question , the greater part being inserted into the cutaneous 

 investment. The second pair of muscles were rather long, thin, and moderately broad. They 

 extended from the lingual bone divergingly and obliquely backwards and upwards to the bony pieces, 

 and clearly represented the mm. omohyoidei, which are also thin in other Saurians, but in relation 

 to their length are of moderate or even of considerable breadth. The muscles of the third pair pass 

 from the two bony pieces backwards and downwards to some of the anterior ribs. They expand 

 fan-like, and may be regarded as the representatives of mm. serrati antici majores of other Saurians. 

 The two remaining pairs lie external to the third pair, but extend further back, and run more 

 obliquely downwards, forming two thin, and anteriorly only small, but posteriorly broader, muscular 

 layers, and were with their broad ends attached to the skin. 



The connection in which the two bony pieces stand with the muscles which correspond to the 

 mm. omohyoidei and to the serrati antici majores of other Vertebrata sufficiently proves that they 

 are to be regarded as scapula?. But their further relations with those muscles which correspond to the 

 sterno-mastoids in their attachments render it probable that they also, in part at least, represent the 

 clavicles [coracoids] . 



I was unable to find any rudiment of a Sternum either in Lepidosternon microcephalum or in 

 the Amphisbcena. 



In Troffonophis Weigmannii, another footless Annulate Saurian, there are two bony pieces 

 similar to those above described. 



According to Rudolph Wagner's drawings, 1 they have a similar form as in Amphisbana fuliginosa, 

 but are proportionally larger, and come into contact below. 



Chirotes canaliculatus (see Plate VIII, figs. 8 10), s the only Annulate Saurian with anterior 

 limbs, not only possesses a Shoulder-girdle, but also a Sternum. According to J. Miiller, who examined 

 and sketched a skeleton of this animal contained in the Paris Museum, the Shoulder-girdle of this 

 animal consists of two bony pieces, which represent the scapula and clavicles [coracoids] . The illus- 

 tration he gives shows that it has a similar form to those of Amphisbcena and Trogonophis, though 

 they are broader at their lower ends, where they are connected with the Sternum. The Sternum [prae- 

 sternum] has the form of a shield, and possesses at its posterior end a much smaller elongated piece 

 of triangular form \meso-xiphisternum] , and with its base turned backwards, as an appendage. The 

 ribs do not appear to be connected with this relatively extremely small sternal bone. 3 



3. Amongst the Snake-like or Atypic Saurii Squamati the Shoulder-girdle and the Sternum are 

 least developed in Acontias meleagris, as far as is at present known. The Shoulder-girdle consists in it, 

 as in the Annulate Saurians, of two simple bones [coraco-scapults} lying on opposite sides of the body and 

 between the lingual bones and the anterior ribs. Their size is, however, proportionately larger than even 

 in the Amphisbtena. In one example, which was nine inches six lines long, the length of each 

 amounted to one line and two thirds, and the greatest breadth to about half a line. They appear as 

 thin plates, moderately broad in proportion to their length, terminating in blunt points and slightly 



1 ' Icones Zootom.,' Leipsic, 1841, pi. xiii, figs. 20 and 22. 



2 The references are made to illustrations in the present work ; there are no figures in Rathke's 

 Memoir. 



3 ' Zeits. f. Physiol. v. Tiedemann und Treyiranus,' vol. iv, p. 259, pi. xxi, fig. 12 b. 



