in Ichthyosauria and Sauropterygia. 239 



Obviously, then, there is small claim to quote Buckland as an 

 authority upon the anatomical details of the pectoral arch. 



Amongst other reasons for suggesting the presence of a precora- 

 coid cartilaginous in Ichthyosaurus assigned by Professor H. Gr. 

 Seeley, are the following, viz. : 



1. " That it accounts for the structure of the shoulder girdle, and 

 explains its homology." 



If by "the structure of the shoulder girdle " the author means, as 

 I imagine, the alleged tripartite division of the ventral end of the 

 scapula, and the marks of attachment of cartilage apparent in the 

 foremost of the supposed three divisions, and also on the antero- 

 internal angle of the coracoid, both are naturally explained in the 

 suggestion I have offered above, and this without the introduction of 

 another skeletal element of which no objective trace remains. As 

 regards the hornologies of all the known parts of the Ichthyosaurian 

 shoulder girdle, I had supposed that all comparative anatomists had 

 long been in perfect accord. 



2. "It brings the shoulder girdle o? Ichthyosaurus into harmony 

 with Nothosaurus, in which there is a similarly incomplete coracoid 

 foramen, and similar cartilaginous surfaces of coracoid and scapula 

 in close juxtaposition." 



The Nothosaurian (osseous) shoulder girdle, for the knowledge of 

 which we are indebted to H. v. Meyer,* comprises three pairs and 

 an azygos piece, viz., two coracoids. two scapulas, two clavicles, and 

 an interclavicle. 



These are precisely the same osseous parts as are present in the 

 Ichthyosaurian shoulder girdle. 



Now, Professor H. G. Seeley inferring the existence of a precora- 

 coid in Ichthyosaurus., supports this hypothesis by the argument that 

 its presence would bring the Ichthyosaurian girdle into harmony with 

 that of Nothosaurus, in which its presence is equally hypothetical. 



The form and the relations of its osseous parts are well seen in 

 the annexed figure from Zittel's ' Palseontologie,' which is a reduction 

 of one-fourth of H. v. Meyer's large figure of the shoulder girdle of 

 Nothos. mirabilis.^ 



H. v. Meyer regarded the two angulated long bones composing the 

 principal part of the anterior ventral ray as clavicles, and the small 

 middle piece embraced by their inner ends as " sternum " (inter- 

 clavicle in the nomenclature of to-day). I formerly thought these 

 precoracoids, but better knowledge of the relation of their inner 

 ends to the interclavicle, and of their outer ends to the scapula, has 



* Meyer, H. v., Saurier des Muschelkalks (' Zur Fauna der Yorwelt,' 1845 

 1857), Fig. 1, Lief. 34, Fig. of Nothos. Shoulder Grirdle viewed from above. Natural 

 size. 



f Zittel, K. A., < Handbuch der Palceont.,' vol. 3, Abth. 1 j S. 476, fig. 447. 



VOL. LII. R 



