280 H. a. SEELEY ON A PORTION OE 



striations. It is separated from the angular by a deep depression, 

 looking as though due to its extension behind the angular, but pro- 

 bably resulting from the elevation of the ornament on the angular 

 bone. The dentary bone makes an angular bend, so as to form a 

 superior surface for the teeth, which appear to look upward and out- 

 ward. "Where the bone ends behind, the jaw extends for 2\ inches 

 below it, and \ inch above it, being 2\ inches deep. 



The angular hone (fig. 1 c) is the most striking part of the specimen. 

 It forms the lower portion of the jaw on both aspects, and is an elon- 

 gated bone tapering towards both ends on both sides. Externally 

 it is 10|- inches long, is received between the splenial and dentary 

 bones in front, and posteriorly becomes depressed and reduced in 

 depth from 1 J inch at 5 inches from the end of the bone, to less than 

 half an inch under the articulation. Its basal border is straight to 

 within the posterior two inches, when it curves gently upwards, ter- 

 minating half an inch short of the surangular bone, which extends 

 along its superior 5| inches behind the point where the dentary bone 

 terminates. This bone is marked by a semicircle of radiated sculp- 

 ture, the centre of which is rather behind the middle of the bone on 

 its basal border. As on the splenial bone, the ornament consists of 

 an irregular honeycomb of pits near the centre, these becoming- 

 elongated laterally into grooves which run towards the extremities 

 of the bone, harmonizing with the sculpture on the splenial and sur- 

 angular elements. The grooves as they proceed become subdivided 

 by ridges, of which five may be counted above the suture with the 

 splenial bone at 8 inches from the end of the bone. The pits and 

 grooves are full of perforations for blood-vessels, which take the same 

 directions as the grooves. A broader groove, also vascular, shaped 

 like the tail of a cursive y reversed, ascends to join the V -shaped 

 groove on the surangular bone, which extends below the articulation 

 of the jaw. These grooves only differ from the others in being 

 broader. Altogether there are about 60 pits or grooves on the an- 

 gular bone, mostly averaging -^ inch in diameter, though some are 

 punctures yL. inch m size; while the broad posterior groove is 

 half an inch in diameter, and the long anterior groove is 6 inches in 

 length. 



On the interior aspect of the jaw the angular bone occupies a 

 smaller area (fig. 2, c). It reaches as far back, but not so far for- 

 ward, as in front, being only about 7| inches long. Its greatest depth 

 is lg inch at 3 inches from its posterior end. The hinder part of the 

 bone is concave from above downward, and has two conspicuous de- 

 scending foramina under the part where it is deepest. 



The surangular element (figs. 1, 2, 3, d) has hitherto been named 

 the articular ; but it extends in front of the articular bone so as to hide 

 the whole of it except the surface seen in the articulation. The 

 branch of the surangular which extends between the angular and 

 dentary bones is about 5| inches long ; but the part which, extending 

 interior to the alveolar margin of the dentary bone, is imperfect an- 

 teriorly, is 8| inches long from the heel of the bone. Superiorly the 

 bone bends over towards the inner side, so as to form a sort of back- 



