12 



OPTHALMOSAURUS PLEYDELLI. 



peculiar to the genus, and may account for the absence of teeth in 

 the jaws of the fine series of Ophthalmosaurian remains in Mr. 

 Leeds' collection. I feel little doubt that the teeth and snout 

 belong to the three-faceted humerus. 



The following is a description of the specimens kindly furnished 

 me by Mr. R. Lydekker : 



"The Ichthyoptery- 

 gian remains from the 

 above-mentioned find 

 the Kimmeridge 



in 



clay of Gillingham 

 sent to me by Mr. 

 Mansel-Pleydell com- 

 prise two propodial 

 bones and three verte- 

 bral centra. One of 

 the propodial bones is 

 much larger than the 

 other. The larger bone 

 is undoubtedly a left 

 humerus, which, in the 

 presence of three dis- 

 tinct facets, is shown 

 to belong to Ophthal- 

 mosaurus as distinct 

 from Ichthyosaurus. 

 The smaller propodial 

 (fig. 1), which is 

 about three - quarters 

 the dimensions of the 

 larger one, appears, 

 however, to be equaUy u ulnar ditta 

 most probable that they bclon 



clearly the humerus 

 of the right side, and 

 as having only two 

 distal facets should 

 apparently be referred 

 to Ichthyosaurus,. 



It appears, there- 

 fore, to be the case, 

 strange as it may seem, 

 the Gillingham re- 

 mains really comprise 

 the remains of two 

 distinct individuals, 

 and accordingly there 

 arises a doubt as to 

 which of the two 

 forms the vertebrae 

 belong. Since how- 

 ever these vertebrae 

 present the same pro- 

 portionate relation to 

 the large humerus as 

 obtains between the 

 corresponding bones 

 of Ophthalmosaurus 

 icenicus, I take it as 

 to the same animal. 



Fig 1. Reversed view of 

 the proximal, dorsal, and 

 distal aspects of the right 

 humerus of Ichthyosaurus 

 sp. from the Kimmeridge 

 clay of Gillingham, Dorset- 

 shire, J nat. size, a trochan- 

 ter ridge, r radial facet, 



I have had recently an opportunity of comparing the Gillingham 

 specimen with a large series of the remains of the typical 0. icenicus, 



