Lect. III.] POUCH-BEARI^'G AXIMALS. 67 



Marsupials, some well known, some less familiar to 

 anatomists, but none of these are aljsolutely wanting in 

 the forms above, nor are there any that cannot be traced 

 to the forms below. 



Yet, fagoted together in the Metatheria, these 

 diagnostics serve the purposes of the classifier, and are, 

 indeed, in their combination, remarkably distinctive of 

 the group. 



Firstly, those parts of the skeleton which are 

 popularly supposed to be so important in relation to the 

 pouch — the marsupial or pre-pubic bones — these are no 

 new thing, but, as we have seen, are equally large in the 

 Monotremes, Y/hich have the pouch rudimentary ; they 

 also exist as pre-pu1jic cartilages in Salamandrians and 

 Skates ; and they reappear, as rudiments, in the Eutheria. 

 The pouch itself — a superficial structure, a mere apron 

 or fold of the skin — reappears, as a rudiment, in the 

 embryo of the Flying-cat of the Phillippines, a sort of 

 primordial Bat, not quite out of the border of the 

 Insectivora. Such a pouch holds the eggs of Pipe-fishes, 

 but it is the male which possesses it ; and some Frogs 

 have such a pouch, but it is on their Ijack. The 

 shoulder-girdle of the Marsupials is quite like that of 

 the highest kind of mammals, in which the clavicles are 

 well developed ; there is no interclavicle between them, 

 and they have a pro-coracoid rudiment at each end, a 

 thin cartilaginous pad. The acromion (shoulder-point) 

 is well-developed, and the coracoid (Crow's beak 



