MAMMALS. 199 



Order "EDENTATA." 



Examples. A. " PHYLLOPHAGA." Bradi/pus? Choltepus. 



B. " ENTOMOPHAGA." Manis, Pltolidotus, Tatusia, Prionodos, Dasypus, 

 Euphractus, Xenurus? Oryderopus, Myrmecophaya, Tamandua, Cyclothurus. 



This is a very difficult group to characterise, for it is extremely polymorphous ; very much 

 more so than the Marsupialia. In the Sloth (Plate XXI) the scapula is very remarkable for the 

 reversed proportions of the " supra-" and " infra-spinous fossae," the latter being the smallest 

 on account of the great relative development of the prse-scapular region (p. sc.). The supra- 

 scapula (s. sc.) has scarcely any separate existence, and in old age it is entirely continuous with 

 the rest of the bone (fig. 13, A'i; fig. 22, Unau). The meso-scapular crest (or spine) arises 

 from but little more than the middle third of the bone (vertically) : in the old Unau (fig. 22) 

 a smaller intermuscular crest ekes it out, somewhat. In the young of both types the acromion is 

 a very long flap of cartilage (figs. 1 and 16, ac.) connecting the meso-scapula with the hook of 

 the arrested coracoid ; whilst the prse-scapular and coracoid regions run into each other in front, a 

 small oval fenestra (c. s. f.) partly cleaving these regions asunder. This continuity is eminently 

 Reptilian, but the elevation of the crest is Mammalian. In the process of growth the acromion 

 becomes less and less in the Ai (see figs. 1, 7, 10, and 13) ; but in the Unau, and in the extinct 

 Phyllophaga, it retains its early condition, and this bridge over the " supra-spinatus" is very 

 strong. The coracoid (cr.) is very large for a Mammal ; and has, exceptionally, an ectosteal 

 ossification, with an epiphysis in its free hook (figs. 10 and 11, cr.) : nevertheless, this does not 

 answer to more than the " head" of the ornithic bone, especially to that part of the coracoid in 

 the typical Bird which sends upwards a strong spur, called by Professor Huxley the " clavicular 

 process," but which does not become free and outstanding either here or in the Struthious Birds 

 and the Reptiles. The clavicle is small in the A'i, and it has not appeared at the time of birth ; 

 both it and the correlated cartilages are best studied in half-grown specimens (figs. 10 and 11). 

 Attached to the blunt hook of the coracoid is the meso-scapular segment (m. sc. s.), for the 

 acromion has retired, and this is somewhat ossified by the clavicle (cl.) ; and at the other end of 

 the clavicle there is a prse-coracoid segment, also partly ossified by the clavicle : beyond this is 



1 I am not aware to what species of A'i the various specimens belonged that I have examined and 

 dissected. The youngest was an almost ripe embryo, the gift of Mr. Mivart ; the figures of it are in 

 PI. XXI, figs. 1 6 ; fig. 7 is from a one-third-grown individual (Hunt. Mus.) ; figs. 8 and 9 another, 

 about the same age (Hunt. Mus.); figs. 10 and 11, half- grown (Brit. Mus.); fig. 12, almost adult 

 (Brit. Mus.) ; figs. 13 15, very old (Hunt. Mus.). The specimens in the Hunterian Museum belong, 

 according to Mr. Flower, to the group termed Arctopithecus by Dr. Gray (see ' Proc. Zool. Soc./ 

 1849, p. 65 73 ; Pis. x, xi). I think it is very probable that in such a low type as this the variability 

 may be very great ; and that the two species of Bradypus and five of Arctopithecus may be diminished 

 when our knowledge is increased. 



3 See Gray, ' Proc. Zool. Soc.,' 1865, p. 359386. 



' Duges, iu his work on the Batrachians, refers to the Sternum of the Kabassou (Xenurus 

 unicinoius, Linn., see the Translation, above, p. 86, where the word is wrongly spelt Kabasson) ; I 

 may again refer to that extract, to show how completely the best anatomists have confounded together 

 dermal and endo-skeletal parts. 



