1882.] PROF. W. H. FLOWER ON THE EDENTATA. 359 



Cuvier's order included the Ornithorhynchus and Echidna, animals 

 of which the structure was then imperfectly known, but which are 

 now by almost universal consent removed to an altogether different 

 section of the class. Otherwise its limits are those now adopted. 

 The name Edentata, moreover, is now so generally used, and its 

 meaning so well understood as a conventional term, that it would be 

 very undesirable to substitute any other for it. In fact similar reasons 

 might be given for ceasing to use nearly all the current ordinal desig- 

 nations of mammals. It might be equally well objected that all 

 the Carnivora are not flesh-eaters, many of the Marsupialia have 

 not pouches, and so forth. 



The few common characters by which the Edentata are associated 

 are too well known to need repetition. The principal one is the 

 absence of any trace of the typical heterodont and diphyodont den- 

 tition, found in a more or less modified form in all other placental 

 mammals \ The one genus Tatusia presents a startling exception, 

 in the presence of a set of milk-teeth, with (according to Burmeister) 

 distinct roots implanted in separate alveoli, and (according to C. Tomes) 

 distinct enamel-organs, if not enamel. This is one of the most im- 

 portant facts bearing upon the evolution of the Edentates yet dis- 

 covered, though its full signification is not yet evident. 



It is highly probable that most, if not all, of the existing Eden- 

 tates are the very much differentiated representatives of a large 

 group, the greater number of which are now extinct, and which 

 have become so without ever attaining a high grade of organization. 

 The great diversity of structure, the high degree of specialization 

 to which many have attained, the paucity of species and even of 

 individuals, their limited area of distribution, and their small size 

 compared with known extinct forms, all show that they belong to 

 an ancient and waning race, the members of wljich still hold their 

 own either by the remoteness and seclusion of their dwelling-places, 

 their remarkable adaptation of structure to special conditions of life, 

 or by aid of the peculiar defensive armature with which they are 

 invested. Their former history can, however, only be surmised, 

 rather than read, at present ; for though we have ample evidence of 

 the abundance and superior magnitude of certain forms in the most 

 recent and post-Tertiary geological age, and in one part of the world, 

 beyond that time {i. e. in the true Tertiary period), and in other parts 

 of the world than America, their fossil remains hitherto discovered 

 are only fragmentary, giving a most imperfect idea of their actual 

 condition, as well as affording no indications that serve to connect 

 them with certainty to any other branch of the class. 



The existing Edentates readily group themselves into five distinct 

 families, of the limits of wliich there is no reasonable doubt. These 

 are : — 1. The Bradypodid.e, containing two genera, Bradypns and 

 Choloepus, 2. TheMYRMECOPHAGiD^E, containingthreedistinctmodi- 

 fications, worthy of generic rank — Myrmecophaga, Tamandua, and 



' The Cetacea are possible exceptions ; but embryological and palsejntological 

 researches appear to show that their dentition may be derived from the ordinary 

 mammalian type. 



