in Iclitliyosauria and Sauropterygia. 247 



The significance of the anterior ventral ray has ever been, and it 

 still is, a "vexed question." I regard it as a precoracoid preserving 

 permanently its original union with the scapula, together with which 

 it shares in forming the fossa glenoidalis. 



Professor H. Q. Seeley considers it part of the scapula. This is 

 plainly shown by the following extracts from his paper: "The 

 scapula is a stout triradiate bone." " In Elasmosaurus the scapular 

 arch has the well-known form with the scapulae meeting in the median 

 line and continuous posteriorly with the coracoids." "The measure- 

 ment of the scapula in the median line is 3| inches." " The 

 scapulaa meet in the usual usual way by a median suture." " The 

 interclavicle was found in situ resting in a depression between the 

 anterior margins of the scapula?." " The interclavicle is wedged in 

 between the scapulae." 



The above passages prove, I submit, that their author rejects the 

 actually dual composition of the bone termed by him, in its entirety, 

 scapula : nor is the significance of these passages weakened by others, 

 as the following, in which the bone is given a compound name, so : 

 " The scapulo-precoracoid appears to form about two-thirds of the 

 wall of the glenoid cavity.'' " It is these precoracoid portions of the 

 scapulce which alone meet each other in the median line." That these 

 last quoted passages may not be understood as implying a shade of 

 doubt in the author's mind respecting the genetic oneness of the ray 

 he calls, in its entirety, scapula, appears to be clear from the follow- 

 ing passage, on the shoulder girdle in certain Plesiosauroids : " In 

 Elasmosaurus, Colymbosaurus, Murcenosaurus, and their allies, the parts 

 of the bone which meet in the median line, and are in contact with 

 the clavicular arch, are theoretically precoracoid* elements which con- 

 nect the scapula3 with the coracoids " (op. supra cit.}. 



It will now be my endeavour to demonstrate that the anterior 

 ventral ray is not only theoretically (whatever precise significance 

 attaches to this term), but that it has an extremely strong claim 

 to be regarded as actually, a precoracoid. 



I shall show that in its position in the girdle, in its relations, and 

 presumably in its genesis, it corresponds essentially to the bone that 

 bears the name precoracoid in extant Amphibia and Reptilia. 



In discussing the homology of the several parts composing the 

 shoulder girdle, we should ever keep before us the elementary fact 

 that the primitive shoulder girdle is originally one cartilaginous 

 "continuum," emitting one dorsal ray and one or two ventral rays. 

 The dorsal ray is, by universal consent, known as the scapula ; where 

 there is only one ventral ray this is by nearly all comparative 

 anatomists known as coracoid ; and where there are two ventral 

 rays, the anterior is designated precoracoid or clavicle. It is con- 



* Italics mine. 



