Prof. Owen on an Ichthjolite from Sheppey. 



25 



fin, which scarcely exists in the Rays. The anal fin is also want- 

 ing in the Hays, it is also wanting in the Torpedos ; but all these 

 fishes have a complete caudal fin, whereas it is wanting in the 

 Rays, as I have just observed. 



I am indebted to the kindness of M. Bibron for being enabled 

 to ascertain that the other fishes alUed to the Rays {Cephaloptera, 

 Myliobates and Pastinacus) whose tail is terminated by a thin 

 and extended whip or prolongation, do not possess this apparatus. 

 The whip is formed of a portion of the tail, which the electrical 

 apparatus would occupy if it existed. 



As we have just seen, this organ cannot be regarded as a 

 gland, for it has not the structure of one ; it does not possess an 

 excretory duct, it does not communicate in any part with the in- 

 side, and no gland receives so many nerves of animal life*. 



IV. — Notice of an Ichthyolite from Sheppey j in the collection of 

 Mr. Tennant, F.G.S. By Prof. Owen, F.R.S. 



The unfrequency of the discovery of any part of the internal 

 skeleton of the cartilaginous fishes associated in a fossil state 

 wath the teeth, which are the most common evidences of the ex- 

 tinct Chondropterygii, induces me to send the following descrip- 

 tion of the Ichthyolite figured in cuts A and B, which has been 

 kindly transmitted to me for that purpose by Mr. Tennant, F.G.S. 

 It was found in the well-known and rich fossihferous deposit of 

 London-clay at the Isle of Sheppey, and consists of a portion of 

 the premandibular bone (c) with six of the large median («) and 

 a few of the small lateral {b) dental plates of the extinct species 

 of Eagle-ray, called by M. Agassiz ' Myliobates striatusJ 

 A B 



Fossil under jaw of Myliobates striatus. 



The first appearance likely to attract attention in the portion 

 of lower jaw here preserved is that of a large medullary cavity at 



• Nevertheless the proof of its being an electrical organ must depend 

 upon its power of giving electric shocks. Such a property, in our common 

 Rays, if it existed, could hardly have escaped the notice of fishermen, in tlie 

 constant habit of handling large Rays, Skates and Thornbacks immediately 

 after their capture. — Ed. 



