1S2 THE ANATOMY OF YERTEBRATED ANIMALS. 



coid is invested, and in part replaced, by a sheath of membrane- 

 bone, which exi3ands above and below, and represents both 

 scapula and coracoid, though it presents no trace either of 

 division, or of a glenoidal cavity. Beyond tlie extremities of 

 this central ossification the cartilage merely presents scattered 

 granular calcification. Along the front edge of each coraco- 

 scapular arch, and closely connected with its ossified part, is a 

 long curved clavicle, entirely cooiposed of membrane-bone, 

 and united with its fellow in the ventral median line, by liga- 

 mentous fibres. There is no interclavicle. The pectoral arch 

 in other snake-like Lizards, such as the Blind- Worm [Angnis) 

 and the Sheltopusik [JPseudojjUs), is in much the same con- 

 dition as in Xiialis. 



"When the hind-limbs are well developed, there is a com- 

 plete pelvis. The ilia are movably articulated with the fibro- 

 cartilages which cover the ends of the sacral ribs. The pubes 

 and the ischia meet in median symphyses, and the anterior mar- 

 gin of the pubis usually, as in the Chelonia^ gives ofi" a strong 

 curved process. In many Lacertilia a partially-ossified or car- 

 tilaginous rod {os cloacce) is continued back from the sym- 

 physis of the ischia, and sup23orts the front wall of the cloaca. 



In most Lacertilia the manus jDossesses five digits ; and, 

 v/hen this is the case, there are usually eight bones in the 

 carpus — one for each metacarpal on the distal side, one radial, 

 one ulnar, and one central. As a very general rule, the pollex 

 has two phalanges, tlie second digit three, the third four, the 

 fourth five, and the fifth three (2, 3, 4, 5, 3). The pes, also, 

 generally possesses five digits, which increase in length to the 

 fourth, the fifth being smaller than the rest, and divergent in 

 direction. Two large bones, very closely united, or complete- 

 ly fixed together, represent the calcaneum and the astragalus, 

 and are articulated, in a manner which allows of very little 

 motion, with the tibia and fibula. In the distal row there is 

 usually a large bone, representing the cuboid. The fifth 

 metatarsal * is bent, as in the Chelonia, and may articulate 

 with the calcaneum as well as with the cuboid. One or two 

 of the cuneiform bones may be present, or the inner ones may 

 be represented merely by fibrous membrane, or by cartilage ; 

 in which latter case the inner metatarsals aj^pear to articulate 

 directly with the astragalus in the skeleton. The number of 

 the phalanges is very generally the same as in the manus for 

 the four tibial toes, but one more for the fibular (2, 3, 4, 5, 4). 



* The bone thus named may perhaps contain a tarsal clement, and repre 

 seut, not only the fifth metatarsal, but the corresponding distal tarsale. 



