REPTILES. 103 



thinner towards the middle than at its edges. In several of these Reptiles it is actually perforated, 

 presenting a space in the centre (Plate IX, figs. 3, 5, and 6), which is closed up by the periosteum of 

 the Sternum extended over it. A similar space or foutanelle of very moderate size and rounded form 

 is apparent at a short distance from the end of the boue in Lacerta ocellata and Seps chalcidica ; a 

 much larger one of roundish form in the middle of the bone in Lophyrus giganteus ; one of considerable 

 size, but of a large oval form, with the long diameter in the axis of the body, in Arneiva vulgaris, 

 Iguana tuberculata (see Plate IX, figs. 5 and 6), Lacerta agilis, Oplurus torquatus, Agama umbra, Ag. 

 colonorum, Phrynosoma Harlanii, Phrynocephalus caudivolvus, and Calotes pictus (Cuv., Agama picta, 

 Pr. Max). If these spaces be not far back, but near the middle of the bone, they are in some cases 

 completely, in others incompletely, covered on the under surface by the anterior sternal bone [inter- 

 clavicle], according as this stem has a greater or less length and breadth (see Plate IX, fig. 2). In other 

 cases, again, the anterior sternal bone does not reach to them nor in any way cover them, which is 

 especially seen in Lacerta agilis, Calotes pictus, Oplurus torquatus, and Seps chalcidica. Sometimes, 

 though rarely, two such spaces appear in the shield-like plate, lying symmetrically, and separated by 

 a small process of bone in the middle line. 



Cases of this kind are presented by Stellio vulgaris (see Plate XI, fig. 2) and Agama mutabilis, 

 in which the spaces are of moderate size and of a long oval form, with the broader end directed 

 forwards. In Uromastix spinipes the number of spaces is still greater, three lying close together, the 

 two lateral spaces [ento-mesosternal clefts] of a long oval form, with their broad ends turned 

 forward and of moderate size ; the middle one [primordial cleft or " fontanelle"] is, indeed, longer, but 

 much smaller, elongated, and triangular, with its basis directed forwards, and completely covered on 

 its under surface by the stem of the anterior sternal bone [inter-clavicle] . 



VIII. According to the statement of Cuvier, in animals of the Monitor species (Varanus) the 

 posterior piece of the Sternum is apparently divided by a fissure, 1 and this statement rests apparently upon 

 Stannius's expression, that in Varanus the posterior piece of the sternum is formed of two symmetrical 

 lateral halves, each of which is cartilaginous. 2 But in three examples of the genus Varanus, particularly in 

 one of V. niloticus, one foot eight inches long, another somewhat larger of V. ornatus, and a third, V. 

 bivitlatus, two feet eight inches six lines long, I have found the plate of the posterior sternal bone which 

 is lozenge-shaped in these Saurians, neither divided longitudinally nor perforate in the centre, yet 

 presenting such an appearance that upon a superficial examination with the naked eye it might be con- 

 cluded that it was composed of two plates of cartilage connected together by fibrous tissue. On its convex 

 under surface, as in many other Scaly Reptiles, there may be seen a moderately broad groove, proceeding 

 from its anterior angle, and extending to a considerable distance behind its middle. At first this is only 

 shallow, but it becomes deeper posteriorly, and is occupied by the posterior half of the anterior sternal 

 bone [inter-clavicle] . Corresponding to this groove and extending over it from behind, is a straight 

 whitish streak (see Plate X, figs. 8 and 10), which completely passes through it from the upper to the lower 

 side. This is small anteriorly, then gradually becomes considerably broader, and then again towards 

 the end of the above-mentioned grooves it becomes smaller till it is no wider than in front, and, 

 finally, terminates in the posterior angle of this lozenge-shaped piece of skeleton. If thin sections of 

 this be now examined microscopically, it appears that the whitish streak in question is only composed 

 of fibrous tissue at its upper and lower side, to wit, from a portion of the periosteum of the lozenge- 

 shaped sternal plate, but in the interior it is formed of hyaline cartilage throughout its whole length 

 and breadth; and that the greater portions of the plate lying on its two sides pass into it without 

 interruption ; these portions, however, only consist of cartilage on their surface, whilst they are bony 



1 ' Recherches sur les Oss. Foss.,' 4th edit. vol. ii, p. 84. 



2 ' Lehrbuch der verg. Anat. v. v. Siebold und Stannius/ vol. ii, p. 138. 



