MAMMALS. 211 



a very large forked acromion (ac., m. ac.), and a very slight differentiation of the supra-scapula 

 (s. sc.). In the Mole (Talpa europaa), which comes nearest the Echidna, the scapula (Plate 



XXVII, figs. 1 3) is extremely high and narrow, and appears to be ossified entirely from one 

 centre, the coracoid process being absent ; for there is a large coracoid cleft away completely 

 from the scapula : the acromion (ac.) and the supra-scapula (s. sc.) are mere polished bosses. 

 The meso-scapular spine (m. sc.) almost dies out in the pinched waist of this phalangoid scapula 

 (see in the young, Plate XXVII, fig. 15, m. sc.) ; the "notch," which differentiates the meso- 

 scapula below, is very shallow (figs. 1 3). Primarily the Mole's scapula (fig. 10, an inner view) 

 is a long, flat ray ; and the only sign of morphological division it has arises from the correlation 

 of the outer surface to the "infra-" and " supra-spinatus " muscles. In the Shrews (Plate 



XXVIII, figs. 1 3, Sorex tetragonurus ; and Plate XXVII, fig. 22, Crocidura ?) the scapula 



is very narrow ; it has a small supra-scapular epiphysis (s. sc.), and another in the small coracoid 

 hook (cr.) ; this latter is early fused into the scapular bone. The meso-scapular spine (m. sc.) 

 is nearly as high as the whole bone is broad (Plate XXVIII, figs. 2, 3, (in. sc.) ; it rises to its 

 highest at the upper third, and leans backwards over the infra-spinous fossa. The notch severing 

 the acromial portion from the neck is very large (fig. 3, ac.) ; and the acromion spreads into two 

 rays with dilated ends (Plate XXVII, figs. 22 and 25, ac., m. ac. ; and Plate XXVII, figs. 13, 

 ac., m. ac.). Of these acromial rays, the foremost (ac.) is tied to the cartilages that surmount the 

 clavicle (cl.), and the metacromion (m. ac.) is free. In Chrysochloris capensis (Plate XXVII, fig. 18) 

 the supra-scapula (s. sc.) is merely a neat upper selvedge of bone, which helps to form the out- 

 spread, pentagonal part of the meso-scapula (m. sc.). At the lower part of the pentagon the spine 

 is of normal breadth ; and it then suddenly sends a large quadrate plate backwards as a roof to 

 the supra-spinous fossa (fig. 19), leans backwards to its base, and for the remaining part is very 

 broad at the top, and forms a large semilunar bar, the terminal third of which is the meta- 

 cromion. The acromion proper (ac.) is marked by an angular process in front of the meta- 

 cromion (m. ac.). The outline of the prae-scapula (p. sc.) is convex, and that of the post-scapula 

 concave ; the former region is the largest, contrary to what is seen in the true Shrews (Plate 

 XXVII, fig. 22 ; and Plate XXVIII, figs. 13). The coracoid (cr.) of the Chrysochlore is a 

 small epiphysis. The general outline of the scapula in the young Hedgehog (Erinaceus europceus) 

 is that of a pruning-knife ; it is not so much bent, and yet it is of the same type of form as that of the 

 Platypus, and, indeed, of a Bird ; the supra-scapular region (s. sc.) being greatly hooked. The 

 two fossae, and therefore the prse- and post-scapulae (p. sc., sc.) are nearly equal ; the meso-scapular 

 spine (m. sc.) is very large, and has an immense acromion (ac.) with a rounded metacromial lobe 

 (m. ac.) : the coracoid region (cr.) is more developed than in the Shrews. The clavicle of the 

 Mammalia (excluding the Monotremes) is always rendered compound by being correlated to certain 

 parts of the Shoulder-girdle ; in the Mole this composition, and the metamorphic processes in- 

 volved in it, are of the highest interest. My earliest Mole-embryos were two or three days old, 

 the next a week or two ; from the study of the earliest I have arrived at the following conclusions 

 as to the structure of these parts. In a very early stage the whole Shoulder-plate is as simple as 

 that of the Clmmseleon (see Plate XI, fig. 4) ; it then undergoes transverse segmentation. The first 

 cleft completely cuts off the scapula from the coracoid mass below (Plate XXVII, fig. 10, gl. cl.); 

 this cleavage is through the glenoid fossa, in the unossified space shown in the figure of the 

 Chamaeleon's Shoulder-plate, between p. sc. and gl. This quadrate mass undergoes further 

 cleavage, for a large slice is cut from it both above and below ; these slices I propose to call the first 



