'574 MR. R. LYDEKKER ON REMAINS [>.'0V. 19 



to a process on the preaxial border, which he identifies with the 

 acromial process of the Monotreme scapula, and marks by the letter 

 e. This process is separated by a deep notch from the glenoidal 

 region of the bone ; and above this process there is a long and deep 

 emargination of the preaxial border (6 of the figure), superiorly to 

 which the distal extremity of the bone is expanded. Now from the 

 absence of any other process between tliat marked e and the distal 

 expansion of the bone, as well as from the general similarity in the 

 position of the process in question, I am inclined to consider that 

 its identification with the acromial process of the ^lonotreme scapula 

 is in all probability correct. If this be so, the pectoral girdle of the 

 Anomodonts will differ from that of the Monotremes in that the 

 precoracoid- — which I regard as the representative of the so-called 

 epicoracoid of the latter — extended upwards to join the acromion. 



In plate Ixix. figs. 5, 6, of his ' Catalogue,' Sir R. Owen figured 

 a portion of the right side of a smaller pectoral girdle, which I have 

 reason to believe belongs to the genus Ptychosiaffurii^ {Ptychognathus). 

 Now in this specimen the scapula gives off a preaxial process for 

 articulation with the precoracoid, which is clearly homologous with 

 the one termed acromial in the preceding specimen, and is so lettered 

 by Sir R. Owen. This acromial process differs, however, from that 

 of Bicynodon in that it is separated only by a groove on the ventral 

 aspect of the bone from the glenoidal region. Above this acromial 

 process there is a shallow notch, on the dorsal side of which there 

 occurs a projection which is shown by other specimens to be the 

 distal extremity of the supraglenoidal portion of the preaxial border 

 of the bone. The relations of these two processes are well shown in 

 the right scapula of Ptijchosiagum orientate represented in Plate LV. 

 fig. 2, where it is quite clear that the upper or supra-acromial 

 process h corresponds to h of Owen's figure. In redescribing the 

 Owenian specimen in the 'Phil. Trans.' for 1888, p. 492, fig. 1, 

 Professor Seeley correlates the process b with the acromion, not 

 mentioning, however, what he would regard as the acromion in 

 the scapula of Bicynodon, where, as we have seen, there is no process 

 in the same position as h, or giving any reasons for his rejection of 

 the determination of Sir R. Owen. Now it will be quite evident 

 from the comparison of figs. 1 and 2 of Plate LV. that the processes 

 marked a and h are homologous with one another, and consequently 

 that a represents the one identified with the acromion in Bicynodon. 

 In describing, however, the scapula of Platypodosaurus (Quart. 

 Journ. Geol. Soc. vol. xxxvi. pi. xvii. fig. 1) Sir R. Owen wrongly 

 identified the supra-acromial process (e of his figure) with the 

 acromial of Bicynodon, regarding the true representative of the 

 latter (y of his figure) as a portion of the glenoidal region ; whereas 

 it will be evident from a comparison of Owen's figure with Plate LV. 

 that his e corresponds with b and his / with a of the latter, which 

 we have shown to be the acromial of Bicynodon. 



If, therefore, the process in the scapula of Bicynodon with which 



the precoracoid articulates is rightly identified with the acromial of 



^ I have proposed this name in place of Ptychogiuithus, which is preoccupied. 



