20*2 MR. E. T. NEWTON ON SOME [Apr. 2, 



which is also in relation with the supraoccipital (s.o.) and with a 

 much smaller bone (pt.ot.) which lies behind it. This plate {sp.ot.) 

 has on its under surface a deep depression, which evidently formed 

 the attachment for the hyomandibular ; the depression is not, how- 

 ever, quite confined to this plate, but seems to extend for a short 

 distance on to the smaller bone which lies behind it. These two 

 bones, therefore, which have combined to support the hyomandibular, 

 are regarded as the sphenotic {postfrontal) and the pterotic 

 {squamosal). 



The last-named bone comes into relation with the supraoccipital 

 on the inner side and has behind it two elements, the outer of which 

 is evidently the post-temporal (^^.?e7n.) and the inner one (/?«.) is 

 either the parietal or epiotic. Another bone which is found behind 

 these in the recent Arius has evidently been lost in this fossil. The 

 post-temporal {jit.tem.) has a peculiar and characteristic structure. 

 On the upper surface of the skull it presents a flattened tuberculated 

 plate, which, a comparison with the recent Arius gagorides shows, 

 is composed of two parts — an anterior, united with the pterotic, and 

 ft hinder one attached to the bone directly on its inner side, the 

 parietal (or epiotic), and extending as far as the supraoccipital. The 

 post-temporal must also have bf en in close relation with the bone 

 behind it, which has been lost ; but the smooth surface now exposed 

 does not indicate a close attachment. The outer extremity of the 

 post-temporal has a very distinct socket for the upper part of the 

 supraclavicular, and from below this a strong bar of bone passes down- 

 wards and inwards quite to the base of the skull, to which it has 

 been firmly attached. There is a thin plate of bone {x) behind this 

 bar, which seems to have been separated from it by the crushing of 

 the skull, that passes backwards and inwards, seemingly to join the 

 broad thin horizontal plate formed by the transverse processes of 

 the vertebrae ; indeed, it may be that this is a j)art of the transverse 

 process, extending forward to join the post-temporal. 



The hinder part of the supraoccipital is wanting, but the front 

 part is preserved and is somewhat shield-shaped, having its margins 

 on each side indented by a series of curves where it is united with 

 the frontal, sphenotic, pterotic, and parietal. The hindermost tem- 

 })oral plate, now wanting, was doubtless also in contact with the 

 supraoccipital. 



The base of the skull is much crushed, but it seems quite certain 

 that the brain-cavity was completely enclosed by bony walls. The 

 buttress-like supports of the post-temporal bones are striking features 

 of this region. Just in front of the left buttress may be seen the 

 remains of an inflated bulla, which lodged one of the large otoliths, 

 and still further forward there is on each side a depression for the 

 attachment of the hyomandibular (Iwu). In front of this again is 

 another pair of elongated depressions, evidently the ethmoid attach- 

 ments for the prefrontals (fig. 2, eth.). The most anterior part of 

 the base, in its present condition, is formed by a fan-shaped mass, 

 which is apparently in part the vomer and in part the ethmoid. 



Three or four of the anterior vertebrae are firmly united to each 



