Zoological Society. 349 



hitherto unrecorded facts to bring forward as in some of my former 

 communications. Tlie very remarkable modifications which this order 

 is seen to present, not only in comparison with the rest of the Mam- 

 malian class, but also among its own members, and the wonderful 

 variety of extinct gigantic species which the New World has yielded 

 to research, have caused the osteology of the group to be more mi- 

 nutely investigated ; while the small number of species and the striking 

 external differences which they exhibit, have left but little room for 

 doubt in the minds of naturalists as to their true arrangement. I will 

 therefore simply point out such of the cranial peculiarities as seem to 

 be characteristic of the order and of its families and genera, dividing 

 it, as appears to me necessary, into five families, since the two forms 

 inhabiting the Old World differ so much from each other, and from 

 the three groups into which those of the New World naturally divide 

 themselves, that although each consists of a single genus, and one of 

 but a single species, it seems requisite that both should stand di- 

 stinct. It will also be necessary to remodel the genera of the Arma- 

 dilloes, and to define them anew by their external characters as well 

 as by those of the skull, since the presence of a tooth in each of the 

 intermaxillary bones of a single species of the family has prevented 

 the essential similarities and diiferences from being duly appre- 

 ciated. 



Although some few naturalists may still associate this order with 

 the true Ungulata, for the sake of keeping the divisions of the class 

 within the predetermined number five, I think that most of those 

 who have given particular attention to the subject will agree, that 

 so natural and strongly-marked a group is well worthy of isolation, 

 which was the opinion of Linnaeus and Cuvier, although the former 

 wrongly associated vnth it a few genera belonging properly to other 

 groups. 



The characters possessed in common by the members of so diver- 

 sified an order, must be expected to be comparatively few ; those 

 which I have observed in the skull are as follows : — 



The tuberosity of the maxillary bone is articulated by the whole 

 of its upper surface to the frontal and orbitosphenoid bones. 



The zygoma is flat and straight, projecting at once outwards and 

 forwards, its articulating surface being more or less confluent with a 

 concavity at the inner side of it which forms a portion of a more or 

 less elongated cone, whose apex would point backwards. In such 

 forms as have the articulation longitudinal, the glenoid surface is 

 distinguishable from that of Rodents by its posterior termination, 

 which is not a thin free edge like the anterior. 



The ahsphenoid bone never extends high, so that the pterygoid 

 ridge forms its upper boundary, or even extends above it. 



The absence of enamel in the teeth, when they exist, must also be 

 named among the cranial characters. 



Fam. 1. Bradypodid^. 



The intermaxillary bones confined to the lower part of the nasal 

 opening ; the maxillary bones provided with simple teeth, shortened, 



