126 SHOULDER-GIRDLE AND BREAST-BONE. 



Tiedemann has stated ('Anatomy and Natural History of the Dragon,' Niirnburg, 1811, 

 p. 14), that Draco viridis possesses six pairs of true ribs, which are connected with the lateral edges of 

 the perfectly lozenge-shaped Sternum. Meckel has also stated (' Syst. of Comp. Anat.,' part ii, 

 section i, p. 432) that in the Draco the six anterior pairs of ribs are attached to the Sternum. But 

 in a skeleton, and in a specimen kept in spirits, I found, indeed, six pairs of ribs lying in the 

 abdominal walls, that presented a strongly arched form, but only three pairs of these actually reached 

 to the Sternum, and were attached to it, on which account I hold that these alone can be considered 

 to be true ribs. 



My own observations (recorded above) are as follows : 



Ribs connected with- An , te t r!or P art With P osterior 



of sternum. part. 



Iguana tuberculata ... 4 pairs. 2 pairs. 



Ltemanclus longipes ... 4 2 



Cyclodus nigroluteus ... 3 2 



Trachydosaurus rugosus . . 3 2 



Psammosaurus scincus ... 2 1 



Monitor draccena . . 2 1 



Hemidactylus ? ... 3 2 



Stellio cordylinus ... 3 



Polychrus marmoratus ... 2 2 



ChamtBleo vulgaris 1 ... 1 2 



C. pumilus .... 1 3 ,, 



Here it is seen that my observations agree with those of Rathke as to the Iguana, the 

 Cyclodonts, the Varanians, and the Gecko; but not with regard to Stellio, 2 Polychrus, and 

 the two Chamseleons examined by me. 



Further observations are needed to show whether some types are really more variable than 

 others, and what is the greatest variation in the adult condition of the most variable tvpes. 



Before describing my own dissection of the Crocodile, I shall give Rathke's important 

 observations. 



RATHKE, 'Brustbein der Saurier,' pp. 20 26. 



XV. In the Crocodiles, or Sauri loricati, the Sternum is composed, as in the majority of the 

 Scaly Reptiles, of two unsymmetrical pieces of unequal size [Sternum proper and inlerclavicle] . The 

 chief segment that possesses considerable length in proportion to that of the body, partly resembles the 

 Sternum of Chamseleonidse in form, partly the chief segment of the Sternum of those Scaly Reptiles in 



In my specimen there was a feebly developed additional sternal rib on the left side (see 

 Plate XI, figs. 4 and 5). W. K. P. 



The union of ribs with the " free sternal horns" which Rathke speaks of (p. 125) must merely 

 be by connective tissue, the line of union being the enlarged longitudinal cleft which first separated 

 the rib from the xiphisternum. 



