NOMKNCI.AIT'RK OK IJtK AmPHIIUAN SllUULUKJt-GlKDLK. 1 Go 



omostenunii of the frog is homoloi^ous with the iiiterchn icle of the 

 li/.ani, which it certaiiily is ii<^t. 



In Parker and Hciswell's text-book tlie confusion is much more 

 glaring. Tlie bony element in the frog is calle<J cjuit** definitely 

 episteruum, and the rounded tip of cartilage otnosterunm. When we 

 come to the sti'ucture of the lizai-d the interclavicle is in tlie figure 

 (p. 299) called ^pisf/^rnntn, and in tlie text m(erc/ain<;fe or eplsterntun. 

 \n the crocodile (p. "^29) it is stated "there is an episternum,'' and in 

 the Plesiosaurs (p. .345) the element is again termed episfernv.m. On 

 p. 485 the element in the Monotremes is called ''pi-sfrn'wtm (iu'er- 

 chividf). Following Parker and Haswell. the student would tlius 

 conclude that the frog's element was the e(jui\alent of i\w reptilian 

 interclavicle, as he would from the stud}' of Sedgwick. 



Reynolds avoids all confusion by consistently calling the median 

 element in the higher forms hiturdauide, but he unfortunately keeps 

 the term episteruum for the frog's element. Thomson is less consistent. 

 In most places he speaks of the iitterdavide, but occasionally of the 

 *' iaterdavide or epistenmm" and in dealing with the crocodile he calls 

 the element '' the so-called interclavicle or episternum," as if there were 

 some <loubt on the matter. By using the term eplsf.eruv,m also for the 

 front part of the frog's element he causes the same confusion, as does 

 >Se«lgwick and Parker and Haswell. 



The solution of all the difficulty is to use Parker's term, (nnonferunni, 

 for the whole median anterior element of the frog. It is the most 

 suitable term, it leads to no confusion, and it is, I believe, the earliest. 

 For the median membrane bone of the higher vertebrates, which in no 

 way corresponds to the frog's element, the term intfi'darid'' should be 

 i)ivariably used, and for the last ten 3'ears at least it has been used by 

 nearly e%ery vertebrate morphologist. The term epinteinum should be 

 dropped absolutely as soon as possible, for while it lasts it can only 

 gi\e rise to confusion. 



The coracoid is one of the elements about which one would think 

 there could be little doubt, and the only doubtful point is whether the 

 cartilaginous lower border should have a special name. Pai-ker called 

 this lower border epicoracoid, and in this he has been followed by most 

 recent writers. But if this lower border is to have a name, the name 

 should not be I'plcoraeoid, as this name was given to the antei'ior 

 coracoidal element of the Monotreme, which no one now l)elieves to be 

 homologous with it. But should a cartilaginous border of any bone 

 receive a special name ? No one ever thinks of giving a special name 

 to the cartilaginous ends oi the long bones, and even when they have 

 special centres of ossification the l)ony ends are only regardeil as 

 epiphyses ; and it seems a mistake evei' to give a special name to a 

 cartilaginous margin unless it can be pro\ed to have s<ime important 

 morphological significance. The only exception to this rule which 

 might be made is where the cai-tilaginous border becomes conspicu- 

 ously developed and is ossified by a special centre, as in the ease of 

 the i^xprascajiida. It thus seems advisable to regard as coracoid all 

 the posterior bony element and the cartilage on its ventral end. 



l2 



