Dr. C. W. Andrews—An Ichthyosaur from Peterborough. 203 
Ophthalmosaurus icenicus described in 1874 by Professor Seeley? from 
a shoulder-girdle and fore-paddle included in the Leeds Collection. 
Recently a number of papers have been published by Knight,? 
Gilmore,® and others on the skeleton of the American Ichthyosaur 
Baptanodon, a contemporary of the English Ophthalmosaurus, from 
which indeed there seems no real reason for separating it, although 
the above-mentioned writers are not of this opinion. 
The restored figure (Fig. 1) of the skull shows that one of the most 
notable characters is the immense relative size of the orbits, which 
occupy practically all the lateral aspect of the posterior region, the 
bones behind and below them (postorbitals, jugal, quadratojugals) 
Fie. 1.—Ophthalmosaurus icenicus, Seeley. Restored skull from right side. About 
4 nat. size. 
ang. angular; art. articular; b.0c. basi-occipital ; dent. dentary ; f. foramen 
between quadrate and quadratojugal; j. jugal; 7. lachrymal; mex. maxilla; 
m. nasal; mar. external nares; par. parietal; pmx. premaxilla; po.f. post- 
frontal; p.orb. postorbital; pr.f. prefrontal; g. quadrate; g.j. quadratojugal ; 
8.ang. surangular ; sc/.7. sclerotic ring; sp/. splenial; sg. squamosal; sé. stapes ; 
3D? 
sup.t. supratemporal. 
forming only a narrow band. Another peculiar feature is the 
presence, on the anterior part of the jaws only, of small, loosely 
attached teeth, which in many specimens are not found, though 
whether teeth were actually altogether wanting in adult animals or 
whether they have been lost after death is uncertain. 
In some of the specimens the condition of the bones forming the 
posterior surface of the skull has made it possible to attempt a restoration 
of this region, of which a number of more or less inaccurate figures, 
mostly from skulls of Zehthyosaurus, have been published. Fig. 2 shows. 
the relation of most of the bones of this region to one another; the 
pro-otic has been omitted because its position is doubtful, and the parietal 
alsoisnotdrawn. It will be noticed that the whole arrangement seems 
to be designed to impart the maximum possible degree of rigidity to 
the quadrates. The stapes (s¢.), which, as usual in the group, have lost 
their auditory function, unite firmly with the basi-occipital by their 
expanded inner ends, while their outer extremities fit into pit-like 
1 Quart. Journ. Geol. Soc., vol. xxx (1874), p. 696, pls. xlv, xlvie 
® Amer. Journ. Sci. (4), vol. xvi (1903), p. 76. 
= Memoirs Carnegie Museum, vol. ii (1905), pp. 77, 325. 
