440 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Juiie 7, 



2. Note on an IcHTnYOSAUEtrs (I. enthekiodon) from Kimmeeidge 

 Bay, Doeset. By J. W. Htjlke, Esq., F.K.S., F.G.S. 



[Plate XVII.] 



On the 22nd December, 1869, I brought under the notice of the 

 Society two fragments of a long, slender snout with sauroid teeth 

 of a peculiar form, obtained in Kimmeridge Bay by J. C. Mansel, Esq., 

 r.G.S., which I was inclined to refer to the genus Ichthyosaurus ; 

 but the evidence not being quite decisive I was obliged to leave the 

 true position of the Saurian indicated by them to be determined at 

 some future time, whenever new material for the purpose might 

 accrue. Meanwhile I gave it the provisional name Enthelciodon, 

 from the thick capsule of cementum surrounding the tooth-fang. 



A very few days afterwards, while making a short visit with Mr. 

 Mansel to Kimmeridge Bay, we discovered great part of the skeleton 

 of an indubitable Ichthyosaurus, the snout and teeth of which agreed 

 so closely with those of Enthelciodon as to leave no reasonable doiibt 

 of their identity, Mr. Mansel generously added it to the splendid 

 series of Kimmeridge fossils already presented by him to the British 

 Museum, and it has lately been placed in the Palseontological 

 Gallery. 



The skeleton lies (as we found it on the reef) on its left side ; the 

 head is bent upwards, the vertebral column makes a double curve, 

 the greater part of the tail is missing, a large number of the ribs on 

 the right side preserve their relations to the vertebral column and 

 to one another nearly nndisturbed ; beneath them is a black stain 

 (cuttle-ink ?), in -vyhich are small scales ; below the early thoracic 

 ribs lie the bones of the breast-girdle, The least mutilated fore- 

 paddle was inadvertently taken from the situation where I saw it 

 before the skeleton was removed by the quarrymen ; and it and the 

 remaining hind paddle have been fixed in the slab below the 

 skeleton. 



The anatomical details of the skuU are not decipherable ; but the 

 orbit is large, and the eyeball has the usual bony ring. 



The entire length of the head is 23-5 inches. The jaws are very 

 long and slender. The teeth are smooth, slender, cylindrical, 

 and pointed ; they are composed of an internal core of simple tubu- 

 lar dentine, the crown overlaid with enamel, and the root enveloped 

 in a thick smooth sheath of vascular cementum, which gives it a 

 bulbous figure. The basal end of the cylinder of dentine contracts 

 slightly, and it is also slightly and irregularly indented, very faintly 

 shadowing, as it were, the beautiful inflexions of the dentine and 

 cementum of the same part in the tooth of /. communis. The apex 

 of the pulp-cavity rises into the crown ; it is filled with a brittle cone 

 of spar ; and the base of the cavity contains a small plug of osteo- 

 dentine, the vascular canals of which inosculate through the open 

 end of the cavity with those of the external sheath of cement, just 

 as in /. communis. 



In the spinal column 56 vertebrae, connected in an unbroken 

 series, now occupy 8 feet ; l)ut the hinder ones have slipped slightly 



