MEGACEPHALTJS AND P. BRACHYCEPHALTJS. 



479 



triradiate bone — when looked at from below, something like the 

 letter j[. The crossbar of the T corresponds to the outer plate of 

 the jugal, the stem to the process which extends from it inwards. 

 The inner plate or process of the jugal does not join the outer bone 

 abruptly, but curves outwards on each side into it. Thus a trian- 

 gular space of considerable size is left at the junction of the two 

 parts, or, in other words, at the origin of the inner plate. This 

 space is occupied by coarsely cancellous bone, and lies immediately 

 under the nutritive foramina, which occur on the outside of the 

 proper jugal bone. The meaning of these foramina is thus made 

 clear. 



The floor exposed by the removal of the jugal is very difficult 

 to interpret. Immediately behind the palatine is a narrow bone, 

 transverse to the axis of the skull, and apparently joining the 

 posterior edge of the palatine. .Behind this, again, is a flat 

 parallel-sided bar or lath of bone, projecting from the middle of the 

 skull outwards at right angles to the axis ; it is united by a splintery 

 suture with the inner margin of a large and important bone, which 

 extends backwards, prolonging the line of the maxilla? towards the 

 quadrate. It consists of a vertical wall-sided outer plate, roughened 

 on the external surface (which is a flat plane), and an interior 

 horizontal plate, the inner angle formed by the divergence of the two 

 plates being neatly rounded into a concave curve. The inner margin 

 of the horizontal plate is a deeply concave curve. 



The vertical plate of a bone having a similar position is shown in 

 the right side of the ventral surface of a skull numbered 14550 in 

 the British Museum. I do not know what to make of this bone ; but 

 it appears to be that which Prof. Huxley has spoken of as quadrato- 

 jugal in his paper on P. Etheridgii. 



The posterior part of the skull of P. brachyceplialus covers over 

 the axis and atlas vertebrae. It consists of the parietal and the ends 

 of the two bones which have been called suprasquamosal. They 

 join in a splintery suture over the middle of the parietal, and appear 

 likewise to underlap it below ; so that this bone appears to proceed 

 from between the upper and lower tables of the suprasquamosal 

 bones. This is a very singular feature ; but as I have been able to 

 examine this posterior fragment of the skull on all sides, and partly 

 to take it to pieces, I entertain little doubt as to its existence. 



2. Redetermination of Measurements. — Professor Owen says that 

 the vertebrae, at least as far as the 28th, are cervical ; but a careful 

 examination leads me to include the 29th as an indubitable cervical 

 vertebra. The succeeding vertebras have lost a slice from their 

 exposed sides ; but there is good reason to conclude that the 30th 

 and 31st also belong to the neck. The length of the cervical series 

 is, then, as follows : — 



I and II concealed+lil to XXIX undoubted cervicals+XXX and XXXI doubtful. 



1-5 inch + 36 inches + 3*5 inches 



=41 inches or 3 feet 5 inches. 



