50G E. TULLEY NEWTON ON THE REMAINS OF 



(pi. 25 6. fig. 3). This, it is said, appears to have belonged to an in- 

 dividual of large size ; the teeth, which are not less than 1| inch in 

 height and -J- of an inch in thickness, are all vertical and very 

 pointed. 



Dr. Mantell's specimens are again mentioned and refigured (pi. 25 6. 

 fig. 1 a, 6). It is certainly somewhat difficult to understand why 

 Prof. Agassiz should have referred all these specimens to one species ; 

 for a comparison of his figures shows a most marked difference 

 between the specimen first described and those subsequently alluded 

 to. If the mandibles represented by plate 25 a. fig. 2, and plate 

 25 6. fig. 3, be compared, it will be seen that in the former the 

 teeth are uniform in size and placed some distance apart ; while 

 those in the latter are very irregular in size and crowded together, 

 some of them being very much larger than the others. The first 

 mandible, as represented in the figure, shows much of its under - 

 surface, its massiveness being as great in a horizontal as in a vertical 

 direction. Anteriorly the ramus narrows as it turns inwards to 

 meet its fellow at the symphysis, so that the front part of the jaw 

 is much narrower, both vertically and horizontally, than is the hinder 

 part. The second mandible (pi. 25 b. fig. 3), although much broken, 

 is evidently seen from the side ; and there can be little doubt that 

 its thickness was chiefly in a vertical direction. 



Again, the maxilla and prsemaxilla of the first specimen (pi, 25 o. 

 fig. 2) differ very considerably from those afterwards alluded to 

 (pi. 25 6. fig. 1). It might be thought that these differences were 

 partly due to the different positions of the specimens ; but such is 

 not the case, for a comparison of the originals (now in the British 

 Museum) shows the differences to be even more decided than they 

 appear to be in the figures. 



In Dixon's ' Geology of Sussex,' published in the year 1850, a 

 small lower jaw is figured (pi. 32 *. fig. 9) ; and although not 

 described in the text, it is named in the references to the plates 

 (p. xiv) Hy_psodon minor. An examination of the original speci- 

 men (also in the British Museum) shows that this mandible, besides 

 being smaller than Aga>siz's type of H. lewesiensis, is proportionally 

 deeper in a vertical direction, and much thinner ; the teeth also have 

 a different character. In all these particulars this little jaw re- 

 sembles the second mandible alluded to by Agassiz (pi. 25 6. fig. 3^> ; 

 and therefore, while the specimens referred to H. lewesi* nsis were all 

 regarded as one species, it was perfectly consistent to refer this 

 jaw to the same genus, although it is now found necessary to 

 remove it to another. 



Prof. Cope has more recently made known to us several new 

 forms of fishes from the Cretaceous Rocks of the Western Terri- 

 tories (see more especially the Report of the U.S. Geological Survey 

 of the Territories, vol. ii. « Cretaceous Tertebrata,' IS 75). To 

 receive these he has found it necessary to establish several new 

 species and genera, which have not hitherto been recognized in this 

 country. In his family Sauron'ontidre he includes six genera, of which 

 he gives the following synopsis (/. c. p. 1S9): — 



