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referring to the peculiar views entertained by each of these ichthy- 

 ologists, he enters upon the investigation of a number of examples, 

 including the Carp, Perch, Gray Mullet, Pike, Salmon, and espe- 

 cially the large scale of an unknown fish from the Bay of Dulse on 

 the western coast of Mexico. The results of this inquiry lead the 

 author to conclusions which differ considerably from those of both 

 M. Agassiz and M. Mandl. He points out the existence of tliree 

 distinct vertically-disposed structures in each of these scales ; a lower 

 one, consisting of membranous lamina ; a middle calcareous one, 

 having a very peculiar structure and growth ; and an upper one, 

 also calcareous, but very distinct from the last, and which is variously 

 disposed in different scales. In all it contributes the peculiar cy- 

 cloid and other markings which ornament their surfaces ; whilst in 

 ctenoid scales, isolated portions of it appear to form the charac- 

 teristic teeth which project from their posterior margins. 



The author then developes in succession the peculiar and beauti- 

 ful structures seen in the scales of Dactyiopterus, Balistes, Loricaria, 

 and various forms belonging to the Ostraciant group. Whilst these 

 examples exhibit singular diversities of structure, they appear to be 

 all modified forms of one common type. 



From this branch of the inquiry the author proceeds to examine 

 the other calcareous tissues existing in fishes, commencing with the 

 endo-skeletons of the Sharks and Kays (Plagiostomes). He shows 

 that the entire osseous elements of these vertebrates are constructed 

 of a peculiar form of bone, which he designates " chondriform," 

 being wholly developed either within the soft tissues of true carti- 

 lage, or of a modified form of cartilage. Fossil remains, having the 

 same structure, have been found in the lias at Lyme Regis and in 

 the coal-measures near Manchester and Leeds. He then examines 

 in succession a number of the bones of the Common Pike, and 

 shows that whilst all the osseous elements of these skeletons are 

 developed in connexion with a cartilaginous matrix, their tissues are 

 of two kinds, which remain permanently distinct. One of these is 

 of the same chondriform character as that seen in the Plagiostomes, 

 being developed in the interior of the cartilage ; the other, which is 

 produced either at the outer surface of the cartilage or in cavities 

 left by the absorption of the latter tissue, the author terms "mem- 

 braniform," being formed within the lamellae of a fibrous membrane, 

 of which the primary origin is doubtful. The peculiar relations 

 which these various structures bear to one another in the different 

 stages of growth are explained. The same process of inquiry is 

 applied to many of the bones of the Perch, Cod, Haddock, Sharp- 

 nosed Eel, Salmon, &c., in each of which peculiarities exist. In the 

 latter example especially the entire skeleton consists of a modified 

 form of chondriform bone, of which it exhibits two kinds. One of 

 these resembles that of the Pike and other examples, both in its 

 aspect and in the situations in which it occurs. The second form is 

 more peculiar ; whilst the way in which its growth is accomplished 

 closely resembles that of membraniform bones produced by the cal- 

 cification of fibrous periosteal membranes, its internal structure 



