1884.] On the Skull in the Mammalia. 81 



But the curious ornithic nasal bones, deeply cleft in front, the im- 

 perfect desmognathism of the palate, the feeble and segmented state of 

 the anterior sphenoid, and the open pituitary space of the embryonic 

 cartilaginous skull, all these things suggest that the Pangolins, "what- 

 ever degenerative specialisation they may have undergone, never did 

 rise to any height, as Mammals. 



Indeed, to me, their pre-natal development the Eutherian placenta- 

 tion seems to be their best title to be ranked even amongst the low 

 forms of the high Mammalia. 



If a complete series of fossil types could be found, on one hand 

 stretching backwards (or downwards) from the Glyptodons, and on 

 the other, from the Megatheroids, then long before these two groups 

 merged into a common Prototherian root-stock, we should find their 

 differences one by one dying out. 



Embryology would help us here very much if materials could be 

 obtained. Even with the scanty treasures that I have been able to 

 obtain, most remarkable things are shown. 



Of the two Anteaters I have only been able to obtain the young 

 (not the embryo) of the smallest and most aberrant type Cycloturus 

 and of the Sloths only two embryos, and one of these considerably 

 advanced, belonging to two genera, namely, Cholcepus and Bradypus 

 (Arctopithecus, Gray). 



But every step backward in the structure of the skull of the 

 Sloth brings me nearer and nearer to what I see even in the young of 

 the Little Anteater ; and that it is possible for both of these types to 

 have arisen from the same stock is no longer a doubtful thing. 



But the skull of developing embryos of the Sloth (of either kind) 

 forms a very valuable and easy- working key to what is difficult in 

 the skulls of the extinct gigantic Megatheroids. 



If this be the case, if Sloths, extinct or recent, have arisen, during 

 time, from the same stock as the great terrestrial Ant-bear, and the 

 little prehensile- tailed Cycloturus, then there is nothing in any other 

 Order to shock the mind or to be a stumbling block in the path of 

 the most timid evolutionist. 



That in the Armadillos the new husbandry, or growth, of hair 

 the correlate of milk glands should thrive badly on the old stony 

 ground of Reptilian horn-covered scales, breaking out where it can 

 among the clefts, is not more wonderful than that this same new 

 growth of hair in the Pangolin should mat itself together and 

 imitate the scales of Reptiles and Fishes. 



I have in the summary to my main paper mentioned several of 

 the most important cranial characters in the Edentata, and have 

 endeavoured to show their signification. 



These, however, have to be studied with the help of the illustra- 

 tions, and need not be spoken of now. Moreover, until the figures 



VOL. xxxvii. G 



