530 5. W. WILLISTON 



no knowledge of the occurrence of all three in other vertebrates. In 

 Lahidosaurus the scapula-coracoid, which has a wonderful resem- 

 blance to these forms, has a distinct supraglenoid opening in the same 

 position, opening internally in the same way with the inner opening 

 of the infraglenoid foramen in a smaller fossa. So, also, in the 

 pelycosaurs there is a corresponding foramen, though it may pierce 

 the bone more in advance of the glenoid depression. In none of these 

 forms, however, have I been able to distinguish a glenoid foramen; 

 certainly there is no inner opening corresponding to that of the 

 amphibians in any of these reptiles. In Varanosaurus the sutural 

 line between the scapula and coracoid (epicoracoid or procoracoid) 

 passes backward through the preglenoid facet, and through the place 

 where the glenoid foramen should be, were there one. The suture for 

 the metacoracoid (coracoid auct.) is back of this place in Varano- 

 saurus. Unfortunately, in none of the amphibians have I, or others, 

 been able to distinguish the divisional sutures between scapula and 

 coracoid in front, or that between the scapula and coracoid and the 

 metacoracoid behind. There can be scarcely a doubt that the extra- 

 ordinary resemblance of the amphibian girdle to that of the cotylosaurs 

 and pelycosaurs extends also to its intimate structure, and that the 

 relations between the scapula, coracoid, and metacoracoid are identical 

 in the two groups. The demonstration of this, however, is not yet 

 possible. What the significance of the glenoid and supraglenoid 

 canals is in the amphibians, the supraglenoid in the reptiles, must 

 await further researches. The latter is present in Iquara. 



The cleithrum or supraclavicle is a much heavier, but more slender 

 bone in Dissorophus than in Cacops. It lies, as in that genus, loosely 

 over the top of the scapula, not suturally united with it, arching roof- 

 like over the top. In front it descends over the rounded superior 

 anterior angle of the scapula, fitting into a depression of that bone. 

 Below, it unites by a long oblique suture with the upper end of the 

 clavicle, extending as a narrow, anteriorly curved process quite to the 

 place where the coracoid turns inward, that is doubtless to the sutural 

 line between scapula and coracoid. 



Various views have been entertained as to the origin, nature, and 

 fate of this bone ; the one usually accepted is that of Gegenbaur, that 

 it represents a like bone in Polypterus; and this seems to be altogether 



