OPHTHALMOSAUEUS. 3 



reception of the species 0. icenicus. The type specimen was a shoulder-girdle from the 

 Oxford Clay of Peterborough : with this there were also associated other parts of the 

 skeleton of the same individual, including portions of the skull, mandible, numerous 

 vertebrae, portions of ribs and neural arches, and some paddle-bones (see Catalogue, p. 63, 

 R. 2133). The feature regarded as specially characterising the genus was the union 

 of the clavicles by suture in the middle line so as closely to embrace the anterior bar of 

 the interclavicle. In the same paper a fore limb of another individual was described 

 and its chief ])eculiarity, viz. the articulation of the distal end of the humerus with 

 three elements, pointed out. It is unfortunate that the type shoulder-girdle is greatly 

 diseased and deformed, the right coracoid being an almost shapeless mass of bone, 

 while the left has a deep posterior notch which is entirely wanting in all normal 

 specimens. The structure of the shoulder-girdle was further discussed by Prof. Seeley 

 in his paper " Further Observations on the Shoulder-Girdle and Clavicular Arch in the 

 Ichthyosauria and Sauropterygia" *. Additional information concerning the genus has 

 been given by Lydekker fj A. S. Woodward J, and Bauer §. The last-mentioned 

 writer has described the occipital and otic regions of the skull from material in the 

 collection now under discussion, but, as will be shown below, his account of the 

 arrangement of the otic elements is not quite accurate. 



The Ichthyosaur from the Upper Jurassic beds of the United States, originally 

 described by Marsh under the name Saiiranodon ||, afterwards emended to Ba]}tanodon%, 

 has lately been the subject of several important papers by Knight **, and especially by 

 Gilmore. Knight describes an imperfect skeleton and gives a number of reasons for 

 regarding Bajptanodon as distinct from Ophthalmosaurus, with which several ^^Titers 

 have considered it as identical. Gilmore first recorded the occurrence of teeth in 

 Baptanodon ff , but in his first note he referred the specimen in which teeth were 

 observed to a new genus Microdontosaurus, a name subsequently withdrawn. He 

 has lately published the most detailed account %% of the skeleton of this form that 

 has yet appeared, and while pointing out that many of the difi'erences between 

 Baptanodon and Opjhthalmosaurus referred to by Knight, do not really exist, and 

 were partly the consequence of the bad state of preservation of the specimens 



* Proc. Boy. Soc. vol. liv. (1893) p. 149. 



t Catal. Foss. Eept. Brit. Mus. pt. ii. (1889) p. 8 ; also pt. iv. (1890) p. 268. 



t 'Vertebrate PaL-eontology ' (1898) p. 18,3. 



§ " Osteologisc-he Notizen iiber Iclithyosaurler," Auat. Anzeiger, vol. xviii. (1900) p. 581. 



II "A new Order of Extinct Eeptiles (Sauranodonta) from the Jurassic Foruiation of the Eoeky 

 Mountains," Amer. Journ. Sci. [3] vol. xvii. (1879) p. 85. Also " The Limbs of Sauranodon, with a Notice 

 of a new Species," loc. cit. [3] vol. xix. (1880) p. 169. 



IF Amer. Journ. Sci. [3] vol. xix. (1880) p. 491. 



** " Notes on the Genus Baptanodon," Amer. Journ. Sci. [4] vol. xvi. (1903) p. 76. 



tt Science, n. s. vol. xvi. (1902) p. 913, and vol. xvii. (1903) p. 750. 



tt ■' Osteology of Baptanodon," Mem. Carnegie Museum, vol. ii. (1905) p. 77 ; also torn. cit. p. 325. 



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