TRANSACTIONS OF THE SECTIONS. 1.21 



On the Myology of Cyclothurus didactylus. 

 By John C. Galton, M.A., F.L.S* 



That wliich Brants (Dissert. Zool. Inaiig. de Tardigi-adis, p. 27 : Lugdun. Batav. 

 1828) has remarked relative to the muscles of the limbs of the Sloths appears to 

 be fairly applicable to the Two-toed Anteater, namely, " Vires motrices anticse 

 corporis partis esse, posticam vero validis musculis ad anteriorem attrahi atque 

 hujus motus sequi debere," — and the more so when we contrast the short hiimeru,<(, 

 rugged with strong muscular ridges, with the long smooth femur, which lacks 

 even a rudiment of a third trochanter. 



In addition to a long prehensile tail (at best but a stunted member in the 

 Sloths), naked for the lower third of its length, the fore and hind feet are marvel- 

 lously modified for arboreal progression, the functional absence of the pollex being 

 compensated for, as Meckel hints, by the enormous development of the pisiform 

 bone, to which are attached numerous strong muscles, while a long strigil-shaped 

 bone, passing baclrward from the scaphoid, more than makes up for the compara- 

 tive shortness of the calcaneal process. 



After the consideration in detail of the muscular system in this and other Eden- 

 tates, the question naturally arises — What zoological value do such details possess? 

 None, it must be confessed. For, apart from their bearings upon the question of 

 the serial and general homologies of muscles, they do not enable us in anywise to 

 simplify and improve the classification, as yet very unsatisfactory, of the members 

 of this much- varying order. 



On the Homologies in the Extremities of the Horse. 

 By E. Gaknek, F.E.C.S., F.L.S. 



The author expressed a doubt whether the cannon-bone in the horse is the 

 metacarpal or metatarsal of the third finger or toe (as the case may be) soleli/ ; 

 and his doubts were derived from comparing the so-called monodactyle animal 

 with the fossil horse, and also with the ox ; from the articulation of the cannon- 

 bone of the horse with two bones of the tarsus (confining himself to the hind 

 limb), the external cuneiform and the cuboid, and from one or two other conside- 

 rations, perhaps of less weight. He questions whether the horse is not monodac- 

 tyle by coalescence, with a trace of the fourth metacarpal or metatarsal ; and again, 

 whether in the ox there is not a trace of the first metatarsal in that part of" the 

 cannon-bone articulating above with the little bone which is probably the first or 

 inner cuneiform. He is hardly satisfied with the usual rendering of the subject in 

 the above and other points, as, for instance, the supposed want of homology between 

 the side hoofs in the hipparion and the little posterior hoofs of the ruminants. 



It does not appear that any use can be attributed to the little horny bodies 

 called chcifaif/nes, which we see in the fore and hind legs of the horse ; they have 

 a musky odour when shaved or cut, and hence they might be supposed to be 

 scent-organs, which, however, is unlikely. They are not merely epidermic, but 

 connected with the cutis vera like nails and hoofs. There are traces of the same 

 parts in all other equine animals, and also of another little horny body called the 

 e7-ffot, or spur, situated at the fetlock, behind the union of the cannon-bone with 

 the pastern. These cannot be reduced to the same category as the callosities 

 or mere epidermal hardnesses, placed where they are of use as protective shields in 

 certain animals, as on the legs and sternum of the camel. The chataig-nes appear 

 to the author to be the vestiges of the nails of the missing great toe and thumb 

 the ergots of the nails of the two minor toes of the fossil horse. In such aberra- 

 tions, as deficient or supernumerary fingers or toes, it is not rare to find a nail to 

 exist where the phalanges have disappeared, and in some individuals a whole row 

 of phalanges has disappeared, whilst all the nails remain normal. The situation 

 of the bodies in question agrees sufficiently with the theory broached. 



* This paper appears in extenso in the ' Annals and Magazine of Natural Historv ' for 

 3tober 1869. ^ 



Octobe: 



