88 SHOULDER-GIRDLE AND BREAST-BONE. 



outer bone, inner bone, and soft cartilage. Duges tripped over this stumbling-stone, and to 

 him a mere ectosteal sheath, the partial investment of a cartilage, stood for a true skeletal 

 element. 



Now, to begin with Duges' description, it will be seen that he is quite right in making the 

 highly developed ad-scapulum (supra- scapula) to be the true representative of the less-developed, 

 epiphyseal supra-scapula of the Mammal ; for ectostosis is never seen in it again, even in the 

 supra-scapula of the Lizards, where it is, relatively, as large as in the Frogs. The scapula and 

 supra-scapula in the Frog are, indeed, two broad " rays," one superimposed upon, and not 

 quite segmented from, the other ; whilst the lower (scapula) has really begun to undergo cleavage 

 in the opposite (vertical) direction ; this partial division into two is borrowed from the Skates. 

 Duges curiously misunderstands the two forks ; for the posterior is not the homologue of the 

 coracoid rudiment of the Mammifera, but the " neck" and glenoid region of the scapula itself. 

 Also the anterior fork is more than the " acromion ;" it contains it, but is properly the prse- 

 scapula ; it might be called the prse-meso-scapula : we shall see this bar differentiated into its 

 proper elements when we come to the Lizards. 



Thirdly, the "paraglenal" of Duges is nothing but the extension of endosteal bone into 

 the synchondrosis which unites and yet separates the three bones that surround the glenoid 

 cavity. 



Then comes the true coracoid, the upper part of which answers to the rudiment seen in 

 most Mammals. The term "coracoidian clavicle" is vicious enough as applied to the coracoid of 

 the Bird and the Frog, but we shall find that it is a most perfect term for the supposed clavicle 

 of the Mole. The fifth piece is excellently distinguished from the true clavicle by Duges, but his 

 name for it is an unsafe one, and his conception of it was confused, for the bony piece is merely 

 the bark of the shaft, the osseo-cartilaginous pith of which he distinguishes, most improperly, as 

 part of another morphological region. My name for the whole band is "prae-coracoid," a name 

 which merely expresses its relation to the better understood posterior bar. Duges is quite right 

 in asserting that these bars do not represent the "furcula" of Birds; and yet, as I shall hereafter 

 show, that compound bone contains rudiments of these bars. He is quite wrong in comparing 

 this bar with what he calls the " acromial " in the Lizards and the Ornithorhynchus ; that bone 

 is the pure clavicle. Sixthly, his " true furculum or furcular clavicle," is made up by putting 

 together the essential part of the right and left prae-coracoids (their osseo-cartilaginous pith) 

 and their continuation below the " epicoracoids," which latter have no ectosteal plate. These 

 two L-shaped bars he supposes to have coalesced to form the " clavicular furculum ;" they 

 seldom unite at the mid-line (see my figures of them in the young Toad, Plate V, figs. 15 17, 

 p. cr., e. cr.) ; generally overlap more or less ; have no splint-bone attached to them, such as 

 forms the " furcula " in most Birds ; and yet there is a grain of truth in the matter, inasmuch 

 as the " furcula" of the Bird does contain rudiments of the " prse- coracoid" cartilages. 



With regard to what Duges says of the pra3-epicoracoids of the Lizards and Monotremes, we 

 there come across this piece of bibliography, namely, that Geoffroy called them " episternals," 

 the sixth skeletal clement which has received that name; whilst Cuvier's sounder judgment refer- 

 red these tracts to the Shoulder-girdle. 



Whilst discussing this part of the Shoulder, Duges, like many other anatomists, confounds 

 together very distinct parts, namely, the "omosternum" of the Frog, the "inter-clavicle" of 

 the Lizard, Crocodile, Monitor, and Ornithorhynchus, and the manubrium of the Mammal. 



