On the Structure of the Palate in Dicynodon, and its Allies. 1738 
plate of the pterygoid is a long median vacuity, lanceolate behind, 
and tapering in front to a slender point. It is defined laterally by 
very slender plates, which converge inward and forward to form a 
single median plate, reaching forward to the maxillary region: and 
this plate may probably be identified as the vomer.” In the same 
paper, however, he describes the almost identically similar structure 
in Dicynodon (pardiceps ?) as part of the pterygoid, and figures the 
median ridge of the premaxillary as the vomer. 
The palatines in Ptychosiagum are fairly well-developed bones 
which form to a large extent the posterior and outer walls of the 
nasal passages. Posteriorly each palatine articulates with the 
lateral wing of the vomer, and along its inferior third it meets on its 
outer side the anterior spur of the pterygoid. From its articulation 
with the vomer the palatine is developed both in a lateral direction 
and anteriorly. The lateral wing passes outwards and upwards to 
meet the jugal. The anterior development passes shghtly outwards, 
and then forwards, meeting and resting on the inner side of the 
maxillary and of the pterygoid. In this region the maxillary sends 
a short plate backwards, which in part lies on the palatine, but is 
mainly separated from it by the anterior spur of the pterygoid. 
Inside of the pterygoid spur and the maxillary the palatine is well 
developed anteriorly, and forms an imperfect secondary palate, 
articulating with the palatine plate of the maxillary. It does not, 
however, meet the vomer or the median ridge of the premaxillary. 
The pterygoid requires but little description; the posterior spur 
to the quadrate and the anterior development to the maxillary 
having been correctly described by Seeley. Though the median 
structure in front of the pterygoids is the vomer there are two small 
delicate plates which rise from the pterygoids and lie on the inner 
sides of the posterior branches of the vomer, forming in part the 
walls of the median vacuity. The bone with which the united 
pterygoids are articulated is evidently the basisphenoid, but the 
anterior continuation of the bone is possibly the presphenoid. I 
have been unable to detect a suture between the parts, but in 
Dicynodon there is a peculiarity in the arrangement of the fibres 
that suggests the probability of the two elements being present 
anchylosed together. 
In Dicynodon and Oudenodon the structure of the palatines and 
pterygoids is very similar to that described in Ptychosiagum, the 
main differences being due to the fact that in Ptychosiagum, as in 
the Cetaceans, the nasal passages lie almost vertically, while in the 
less specialised types the passages pass as in land mammals in an 
antero-posterior direction. 
