512 E. TTTLLEY NEWTON ON THE REMAINS OF 



PORTHETJS GATJLTINTTS, 11. Sp. PL XXII. figs. 1-12. 



Mrs. Elizabeth Warne has recently enriched the Museum of 

 Practical Geology by the presentation of a very fine specimen of a 

 Portheus, which was obtained through Mr. E. Charlesworth, from 

 the Gault of Folkestone. This specimen includes the greater part 

 of upper and lower jaws of both sides, with a considerable portion 

 of the brain-case and bones of the ethmoidal region, also several 

 vertebras and fragments of bones which cannot be identified. The 

 generic relationship of this specimen to the American Portheus 

 cannot be doubted ; specifically it is so closely allied to P. lestrio, 

 Cope, that oue might at first be inclined to refer it to that species ; 

 but, besides its much smaller size, it exhibits certain peculiarities 

 which prevent its being regarded as the same. Each of the parts 

 will now be considered separately. 



Maxilla and Prcemaocilla. — These two bones are represented by 

 Plate XXII. figs. 2 and 9, moc <fc pnuv; they are so closely fitted together 

 that, it is evident, no movement could have been possible between 

 them. The maxilla extends forwards on the inner side of the prae- 

 maxilla to within an eighth of an inch of the front border of the 

 latter bone, which thus comes to lie altogether upon the outer side 

 of the maxilla. The outer surface of the praemaxiila is convex ; its 

 hinder border is deeply and irregularly serrated, so that its junction 

 with the maxilla is very distinctly seen. At the lower part of this 

 junction there is a groove which terminates in a deep notch upon 

 the dentary margin. The anterior border is convex, and terminates 

 above in a rounded process ; immediately behind this, and therefore 

 upon the upper margin, there is a notch, from which the upper 

 border curves backwards and downwards, and is continued into the 

 serrated posterior border. The dentary margin appears nearly 

 straight in a side view ; from below it is seen to be provided with 

 five alveoli (PI. XXII. fig. 9), the second and third being much larger 

 than the others ; and the teeth which they supported were probably 

 not less than an inch in length, as indicated by the dotted lines 

 (PL XXII. fig. 2). Upon the left side the 1st, 3rd, and 4th alveoli 

 support functional teeth, while in the 2nd the tooth has scarcely 

 reached the level of the margin, and the 5th seems to be occupied 

 by bony matter. Upon the right side the 2nd, 4th, and 5th have 

 functional teeth, while in the 1st and 3rd the teeth have not 

 reached the level of the margin. 



It has already been pointed out by Prof. Cope, that Portheus had 

 a vertical succession of its teeth ; and this is well shown in the 

 present specimen, both in the pramiaxilla, maxilla, and mandible. 

 While the teeth were being thus continually renewed, the alveoli 

 supporting them appear to have been persistent ; and not only so, 

 but they seem to have maintained their relative sizes ; for while 

 some of the alveoli are completely filled by the fangs of the teeth 

 they support, others, of equal size, contain teeth in various stages of 

 growth, and not nearly filling their cavities. 



Apparently as a consequence of this vertical succession, the teeth 



