106 SHOULDER-GIRDLE AND BREAST-BONE. 



instance, diverge from one another, then again closely approximate, and form either a pair of flat 

 arches or a pair of very obtuse angles, leaving an elongated space between them, which is broadest 

 about its middle, and has the form of an ellipsoid, or of a lozenge, or of a moderately broad fissure. 

 This space is occupied by a layer of fibrous tissue. 



They present such a course and form in Tejus Teguixin, Lacerta agilis, Lacerta ocellata, Platy- 

 dactylus guttatus, Platyd. aegyptiacus, Euprepis Merremii, and Euprepis bislriatus, in all of which, more- 

 over, they are at their extremities united at angles of varying degrees of obliquity with one pair of 

 ribs, their extremities being turned towards the middle line of the body. In others, again, as in 

 Varanus niloticus and Agama umbra, they are deflected outwards, separate more and more from one 

 another, and form with one pair of ribs well-marked arches. 



lu the Saurians mentioned in this paragraph, in which the length of the sternal horns were 

 determined with perfect or nearly perfect accuracy, they were for the most part smaller than in 

 those mentioned above ; but in the several species their length was to the length of the sternal 

 plate 



In Varanus ornatus =. 0'18 



Varanus bivittatus = 0'22 



Lacerta agilis = 0'57 (to 0'75) 



Tejus Teguixin =r 0'61 



Calotes pictus = 0'65 



Lacerta ocellata = 0-66 



Platydactylus cegyptiacus =. - 71 



Euprepis bistriatus = 0-71 



Agama umbra = - 80 



Iguana tuberculata =^ 0'87 



Polychrus marmoratus = I'OO 



,, Cyclodus nigroluteus = I'OO 



Platydactylus guttatus =. 1*12 



Euprepis Merremii =1 1'14 



XII. An asymmetrical appendage [xiphisternum] to the posterior sternal bone [meso-sternum] 

 appears, from the foregoing observations, to occur in a much smaller number of Scaly Lizards than a 

 pair of symmetrical appendages. I have remarked the former only in Gongylus ocellatus, Ameiva 

 vulgaris, and Chamasaura anguina. In all three it consists of a bony plate, which OH one side is 

 curved upwards and on the other downwards. In Gongylus ocellatus this plate has the form of an 

 elongated lozenge ; but the edges were moderately concave, and the extremities somewhat truncated. 

 Their length is proportionate to that of the posterior sternal bone [mesa-sternum] , to the end of which it 

 was fastened, as 0'74 : 1. In Ameiva vulgaris it has the form of a pentagon, with an angle directed 

 forwards, whilst the two angles that were directed backwards were prolonged into two short horns, that 

 were connected with the ends of two ribs by a short band of connective tissue. 



Including these horns, the proportion in length of this piece to the anterior division of the 

 posterior sternal bone was as 0'82 : 1. 



In Chamtesaura anguina it was about as long as the posterior sternal bone, and was not, as in the 

 preceding animals, connected with it through fibrous tissue, but was so coalesced with it that it 

 appeared only as a prolongation of that bone. Their anterior and posterior halves formed two triangles 

 with concave borders, whose anterior angle (Scheitelwinkel) is turned forwards, and the remaining 

 angles are connected with a corresponding number of ribs. In the middle of the anterior half I found 

 a small roundish space filled with fibrous tissue. 



