92 SHOULDER-GIRDLE AND BREAST-BONE. 



arched on their flat surfaces. They have an oblique direction from above downwards, backwards, and 

 inwards. They lie on the two sides of the oesophagus and trachea, and approximate so closely to 

 one another under the latter that the breadth of the space intervening between them is less than the 

 diameter of the trachea. At their lower ends they are connected with one another by a very thin but 

 strong strip of fibrous tissue, which attaches them together beneath the trachea. Three pairs of 

 muscles are connected to them, two are comparable to the omohyoids, and are of moderate length and 

 breadth, but very thin. These muscles about the middle of their extent have, like the muscles bearing 

 this name in many other Scaly Reptiles, a transverse small tendinous intersection (inscriptio tendinea). 

 They proceed from the horns of the lingual bone straight back to the bones in question, attach them- 

 selves to nearly the whole length of those horns, and lie, as is frequently the case in the Scaly Reptiles, 

 so close to one another that the trachea can -only just be seen between them. 1 Two shorter and 

 much smaller but thicker muscles than the former extend from the lateral parts of the cervical 

 vertebrae obliquely backwards and somewhat downwards to the upper ends of the two bones, and 

 correspond to the levatores scapularum of other Scaly Reptiles. The muscles of the third pair pass 

 from the five anterior pairs of ribs forwards to the bones, and consist of two bundles of moderate 

 breadth and thickness, and are the serrati antici majores of other Reptiles. But there are yet 

 other muscles which are not attached to the two bony pieces, because the three pairs already 

 mentioned correspond only to those muscles of other Vertebrata which are adherent to the 

 scapula. These bones are also to be regarded as simply scapulae. Close behind the posterior 

 extremities of the small scapulae, imbedded in a thin layer of fibrous tissue, and situated also behind 

 the approximated anterior extremities of the muscles corresponding to the serrat. ant. maj., which are 

 attached to the most anterior pair of ribs, there may be found in Acontias meleagris two bony plates [pra- 

 sternum] of elliptical form lying in close proximity to one another, the length of which did not amount 

 to quite a quarter of a line even in the largest of two specimens that I dissected, which measured nine 

 inches six lines. From their position they might be regarded as rudiments of a Sternum. As the 

 earthy salts had been withdrawn from them as a consequence of maceration in hydrochloric acid, small 

 groups of two to four cartilage-cells could be discovered in the remaining cartilage. 



4. In the remaining atypical Scaly Reptiles examined, viz. Ophisaurus ventralis, Anguls fragilis, 

 and Pseudopus Pallasii, both the Shoulder-girdle and the Sternum are developed to a considerably 

 greater extent than in Acontias meleagris. According to the statements of Heusinger, 2 J. Muller,s and 

 Stannius, 4 the Sternum is wanting in Anguis and Ophisaurus, but these statements have been cor- 

 rected by G. Cuvier in the second edition of his ' Le9ons d'Anat. Comparee/ vol. i, p. 253. 



In all three species of the above-mentioned Scaly Reptiles the Sternum is composed of two 

 azygous (unsymaietrical) pieces very different in form and size, the smaller one [inter -clavicle] lying 

 under the larger, and firmly connected with it by fibrous tissue. The larger one [pr<e -sternum] is a 

 tolerably long but thin plate, whose transverse diameter is the longest, and is on its tipper surface 

 slightly concave from right to left, and on its lower surface slightly convex. In Ophisaurus the form 

 of this plate is oblong, but it is slightly excavated at its extremities as well as at its posterior border. 

 In Anguis (see Plate VIII, figs. 6 and 7, st.), the ends are bluntly pointed, and it is excavated to a 

 tolerably broad and deep extent both at its anterior and posterior borders. In Pseudopus it was nearly 

 in the form of the longitudinal section of an olive, i. e. it is slightly convex at its anterior and posterior 



1 The sternohyoids are wanting. 



2 'Zeitschrift f. Organische Physik,' B. iii, p. 496. 



3 ' Zeits. f. Physiol. v. Tiedem. and Treviran./ B. iv, p. 227, 1831. 



4 ' Lehrbuch du vergleich. Anat. v. v. Siebold und Stannius,' B. ii, p. 139. Berlin, 1846. 



