18 PROCEEDINGS OF SOCIETIES. 



Mr. Kennedy exhibited some specimens of Enteromorpha intestinalis, from 

 the Paisley canal, in general, a littoral species ; but in this instance some- 

 what remarkable, from its inland habitat. 



Mr. Robertson exhibited a specimen of Desmarestia herhacea, collected 

 floating near Moville, Ireland, by his friend, Mr. Sawers. Mr. Sawers re- 

 marks, that, in a letter received from Mrs. Griffiths, Torquay, concerning this 

 species, he is informed that Agardh had pronounced this i)lant, after com- 

 parison with Russian specimens, to be undoubtedly D. herhacea, though the 

 foreign specimens were much larger, and the lateral frondlets more fully 

 developed. 



Mr. Robert Gray then stated to the meeting, on the authority of his friend, 

 Mr. Sinclair, the occurrence of Larus eburneus, at Ailsa Craig. As, however, 

 no specimens had been shot, the secretary remarked, that such statements 

 coming before the society should be received with the usual caution, till an 

 opportunity of verifying the fact, by examination, should occur. 



The honorary president, Dr. Scouler, of Dublin, then read a Paper on the 

 Structure of the Teeth and Jaws of the Fossil Fishes of the Cartilaginous 

 Order. He opened the subject by giving an outline of the history of the 

 Ganoid fishes, both living and fossil. " The order of Ganoids of Agassiz," he 

 remarked, "is equivalent to cartilaginous fishes, with the exclusion of the 

 Acipenseres or Sturgeons, which have been removed by Agassiz from the 

 class of cartilaginous fishes, and placed near the Siluroids, with which they 

 appear to have many ailinities. From the cartilaginous natui-e of their 

 bones, it is very rarely that any portion of the skeletons of Ganoid fishes is 

 found in a fossil state. On the other hand, their teeth and spines occur in 

 great abundance, and by the aid of a knowledge of existing species, afford 

 means of classifying them according to their affinities. The Placoid fishes 

 are arranged under the orders of Petromyzons or Lampreys, of which no 

 fossil species have yet been found; — the Sharks, the Rays, and the Chi- 

 mseras, of which numerous remains are found in the strata of every age. In 

 common with other classes of extinct animals, they appear to be regulated 

 by certain laws of distribution. The Chimaeras are not found in the older 

 fossilliferous strata, but chiefly in the newer secondaiy and the tertiary. 

 A similar law, upon the whole, holds good with regard to the Rays or flat 

 cartilaginous fishes. The order of succession in these fishes is, however, 

 better seen in the succession of the diff'erent divisions of the great family of 

 Squalids or Sharks. The Sharks are divided into three groups, viz., the Ces- 

 tracean, with flat teeth for bruising their food ; the Hypodonts, with com- 

 pressed and obtuse teeth; and the true Sharks, with sharp cutting teeth. 

 The Cestraceans are veiy abundant in the carboniferous limestone and coal 

 formation ; they then disappear, and, at present, we have only one living 

 representative of this division— the New Holland Shark. In this respect, 

 the Cestraceans resemble the Cephalopods with chambered shells, which 



