Huxley— On a new Reptile from the Chalk-marl. ^ Q5 



IV. — On Acantbopbolis Horridus, a New Eeptile from the 



Chalk-makl. 



By Thomas H. Huxlet, F.R.S., V.P.G.S., 



Professor of Natural History ia the Eoyal School of Mines. 



PLATE V. 



SOME time since, my colleague, Dr. Percy, purchased from Mr. 

 Griffiths, of Folkestone, and sent to me, certain fossils from the 

 Chalk-marl near that town, which appeared to possess unusual 

 characters. On examining them I found that they were large scutes 

 and spines entering into the dermal armour of what, I did not doubt, 

 was a large reptile allied to Scelidosaurus, Hylceosaurus, and Pola- 

 canthus. I therefore requested Mr. Griffiths to procure for me every 

 fragment of the skeleton which he could procure from the somewhat 

 inconvenient locality (between tide-marks) in which the remains had 

 been found, and I eventually succeeded in obtaining three teeth, with a 

 number of fragments of vertebrae, part of the skull and limb-bones, 

 besides a large additional quantity of scutes. I am still not without 

 hope of recovering other parts of the skeleton ; but as the remains 

 in my hands are sufficient to enable me to form a tolerably clear 

 notion of the animal's structure, a brief notice of its main features 

 wiU probably interest the readers of the Geological Magazine. 



The dermal bony plates or scutes (Plate V. Figs. 1-3) are of very 

 various forms and sizes, from oval disks slightly raised in the middle, 

 and hardly more than an inch in diameter, up to such great spines as 

 that represented in Plate V. Fig. 1, which could have fallen little short 

 of nine inches in length and five inches in the antero-posterior mea- 

 surement of its base. The outer surface of all these scutes is irre- 

 gularly pitted and, in the case of the long spines, is occasionally 

 marked by branching grooves which doubtless lodged vessels. 



Each scute is excavated on its attached face in proportion to the 

 elevation of its outer surface, so that a transverse section of one of 

 the depressed scutes is more or less roof-like, while that of one of the 

 long spines shows it to possess a great internal cavity like the 

 medullary cavity of an ordLaary bone. 



Some of the scutes, though comparatively few, are almost flat, 

 with an obtuse median ridge, which is highest about the middle of 

 the scute (Plate V. Fig. 3). But when the ridge is more prominent, 

 as in Plate V. Fig. 2, its summit is usually placed very much nearer 

 one edge than the other, so that one side of the triangular lateral 

 aspect is much shorter and more perpendicular than the other. 

 The short side, however, is not absolutely perpendicular in any 

 scute among those which have reached me, and the summit con- 

 sequently always lies within the circumference and never overhangs 

 it. 



The spine-like dermal plates are altogether unsymmetrical. If, 

 as I suppose, the convex edge of that represented in Plate V. fig. 1 

 was anterior, then the posterior edge is concave, and the left side convex, 

 with a slight longitudinal excavation in its anterior half; while the 



VOL. IV. — NO. XXXII. 6 



