UPON HYPEKODAPEDON GOEDONI. 



679 



of the V being turned forwards. The most anterior two of these 

 are 4-5 millim. broad in the middle ; but, behind, they become 

 narrower in the middle and taper off to mere threads of bone at 

 their outer and posterior ends. This area of Y-shaped ossicles can 

 be traced back for 90 millim. and is fully 120 millim. wide. Between 

 the 15th and 20th vertebrae, narrow and nearly straight bands of 

 bone appear to extend across the abdominal wall, and either to end 

 in, or be connected with, the lateral ossicles already mentioned. 

 The width of the area occupied by the abdominal ossicles, in this 

 region, is not less than 220 millim. In front of the right pubis 

 there are three broad curved plates, the inner ends of which turn 

 forwards, and which fill up the space between the praepubic process 

 and the position which would be occupied by the epipubic cartilage, 

 if such existed. The posterior abdominal ossicles in Crocodiles are, 

 as is well known, closely connected with the pubis. Splienodon 

 requires re-examination in relation to this point. 



The sacral vertebrae are, unfortunately, much injured; but the 

 centrum of the first (Plate XXYI. fig. 10) appears to be amphi- 

 ccelous, the convex posterior face of the 23rd (or 24th) centrum 

 fitting into it in front, and the convex anterior face of the second 

 sacral fitting into it behind. 



The rib of the first sacral vertebra measures 18 millim. trans- 

 versely, and its expanded outer end 23 millim. 



In the form of the articular surfaces of the centra, in the great 

 development of the cervical ribs, and in the absence of intercentral 

 ossifications, the skeleton of the trunk of Hyperodapedon departs 

 from Splienodon more widely than in any other particular. 



The skull has been completely detached from the matrix, and all 

 its most important characters are beautifully displayed. 



Yiewed from above (Plate XXYI. fig. 1), its contour presents the 

 form of a broad-based isosceles triangle. The base, represented by the 

 occipital region, measures 210 millim. ; while the distance from the 

 centre of that region to the rounded apex, formed by the conjoined 

 premaxillary bones, is 160 millim. The hinder moiety of the dorsal 

 region of the skull displays the great supratemporal fossae (s.t), which 

 are somewhat rounded (50 millim. wide and 58 millim. long), and are 

 separated by the relatively narrow parietal region of the skull (20 

 millim. wide), which presents no parietal foramen. In the front 

 moiety, the orbits (or.), of a half-oval shape (50 millim. long and 

 30 millim. wide), are separated by the broad frontal portion of the 

 skull, which is 40 millim. wide. In front of these, again, and of the 

 broad and short nasal bones, is the single anterior nasal aperture (a.n), 

 which is triangular, with the apex forwards, and is 20 millim. broad 

 by 24 millim. long. In the living animal, this opening would have 

 been divided into two by the nasal septum ; but, no doubt, this was 

 entirely cartilaginous, and hence, in the fossil, the aperture appears 

 single. Laterally, it is bounded by a strong ascending process of 

 each premaxilla. 



In this respect there is a very marked difference between 

 Hyperodapedon and Splienodon. In the latter, the median end of 



