51 



cleus and an external spherical shell are in a state of dilatation, and 

 that a shell intermediate between them is in a state of contraction ; 

 that its structure and optical properties are not alike in all directions, 

 but have reference to the axis of vision ; and that its peculiar struc- 

 ture probably is necessary for correcting spherical aberration. 



Some farther Account of the Fossil Remains of an Animal, of which a 

 Description was given to the Society in 1814. By Sir Everard 

 Home, Bart. V.P.R.S. Read June 13, 1816. [Phil. Trans. 1816, 

 p. 318.] 



The present descriptions are taken from specimens hi the collection 

 of Mr. Buckland of Oxford, and Mr. Johnson of Bristol, and are 

 thought to determine the class to which this animal belongs. 



The structure of the vertebrae, as shown in the author's former 

 paper, made it evident that the progressive motion of the animal re- 

 sembled that of fishes ; but at that time neither the scapula in its 

 perfect state had been seen, nor had the bones of the pectoral fin been 

 found, which now make it clear that all the bones correspond with 

 those of fishes, but differ essentially from those of land animals. 



In all animals that breathe by means of lungs, the ribs are articu- 

 lated both to the bodies and to the transverse processes of the ver- 

 tebrae, so as to admit of expansion of the chest ; but the ribs of fishes 

 which solely give defence to the viscera, have only one insertion, 

 being connected solely with the bodies of the vertebrae, midway be- 

 tween their two articulating surfaces, so as not to interfere with the 

 motion of the vertebrae on each other, as is the case in land animals. 



The author observes, that the ribs in this animal are placed in all 

 respects like those of fish. 



In the whale tribe the scapula and bones of the fore fin resemble 

 those of the crocodile, and they bear a close analogy to those of land 

 animals in general ; but in this animal these bones, it is observed, 

 resemble those of the shark. 



It is remarked also, that the bones in the young state have epi- 

 physes, as is the case with the bones of fish generally. The ribs 

 also appear to have been soft like those of fish, as we may judge from 

 the grooved or fluted form, they have assumed by compression. 



But though, from consideration of all these circumstances, Sir 

 Everard Home has no doubt that this animal was a fish, he admits 

 that the long projecting snout and conical teeth show a marked dif- 

 ference between this animal and any now in existence, and may oc- 

 casion a difficulty in arranging it with any class of known animals. 



Farther Observations on the Feet of Animals whose progressive Motion 

 can be carried on against Gravity. By Sir Everard Home, Bart. 

 V.P.R.S. Read June 27, 1816. [Phil. Trans. 1816,^. 322.] 



Since the author's former observations on this subject were com- 

 municated to the Society, he has been enabled, by the assistance of 



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