590 PROF. G. B. HOWES ON THE CORACOID [Juue 20, 



young of members of six orders of Placental Mammals (see the list 

 given below). I give iigures of some of my specimens, and it 

 ^\^ll be noticed that there is evidence of independent parallelism 

 of reduction of the bone named. The conditions suggest that 

 the differences between the Choloepus and Bradypus figured may 

 be akin to those between Cehus and Homo, Lepus and Scmnis, and 

 that the Edentata may be on a variational equality with other 

 orders in respect to the reduction in question. 



To turn finally to the M'ell-known overgrowth of the Edentate 

 epicoracoid and scapula, for enclosure of the so-called coraco- 

 Bcapular foramen. Lydekker merely alludes to the similarity in this 

 respect between the Edentates and Dicynodonts. So far as I 

 am aware, this peculiarity is invariable only in certain Edentata 

 and Cebidse \ among living Mammals, and a similar condition is 

 well known to occasionally occur in Man. Prof. Bland Sutton 

 has instituted comparisons ^ between the human blade-bone thus 

 modified and that of the Sloth, and in so doing he has remarked^ 

 "I am disposed to the view that the transverse ligament in Man 

 is the fibrous representative of this bony bridge constant in Sloths, 

 and that the occasional occurrence of a complete osseous foramen in 

 this situation is not to be regarded as an ossification of the transverse 

 ligament, but as a reversion to a former condition." The known 

 facts of morphology lend no support whatever to this view. AVere 

 it tenable, the embryonic scapula of Man should bear an expanded 

 if not an actually perforated prescapular lamina, which it does not *. 

 The entire absence of the prescapular lamina in the Monotremes 

 and Anomodontia, and the fact of its known increase of expansion 

 during development in Man and in some few other Placentalia, go 

 far towards proving that its overgrowth to meet the epicoracoid must 

 be in all cases secondary ; and they testify to an independent paral- 

 lelism of modification in the two great classes of animals. The 

 condition occasionally met ^\^th in Man may be closely paralleled 

 by the Tapir among placental quadrupeds. 



The Bradypodines are remarkable for the secondary association 

 of the clavicle with the coracoid (see above, p. 586). In the Choloe- 

 pines the cyjf.r of the acromion becomes inwardly rotated, and, 

 together with the clavicle and coracoid, bound up in a dense fibro- 

 cartilaginous mass '. In Cycloturus the scapula differs from that 

 of all other Edentata but some Armadillos (ex. Dastjpus minutus) 

 in the inward rotation of its antero-ventral border. As viewed from 

 the front (see fig. 2 6, p. 591), this is very conspicuous. I find, on 

 examination, that this peculiarity is associafed with the presence of 

 a very powerful ligament Qg.) which passes between the hodij of the 

 adult acromion and the scapida, enclosing a foramen above. In 



* In Ateles marginatus (&g. 1 h) (not in A. melanochir), Brachyieles, and 

 Lagothria:. 



"■' ' Ligaments, their Nature and Morphology.' Loudon, 1887. 

 ' Op. cit. p. fS. 



^ Cf. Parker's Eay Soc. Monogr. pi. xxx. figs. 9 and 12. 

 ' Cf. Parker, op. cit. pi. xxi. figs. 10 and 2'.i. 



