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Work o/'Agassiz on Fossil Fishes.* 



Of the great work on " Fossil Fishes,'"* by Professor Agassiz, 

 four numbers have already appeared, eminently distinguished 

 by the accuracy and elegance of the engravings, and the very 

 interesting nature of the letterpress. The fifth number is fi- 

 nished, and will appear during the course of next month. 



In the first number our author informs us, that, by an atten- 

 tive examination of the scales, fishes may be divided into orders 

 more natural than those hitherto adopted by naturalists. In 

 this manner he has established four orders, which bear some re- 

 lation to the divisions of Artedi and Cuvier, but one of which, 

 hitherto misunderstood, is almost exclusively composed of gene- 

 ra whose species are found only in the older formations of the 

 crust of the earth. These four orders are the following : — 



Order I. Placoides. — The tribes of this order are so named on 

 account of the irregularity of the solid parts of their integuments ; 

 these are, masses of enamel, often of considerable size, or sometimes 

 reduced to small points, as in the shields of the ray and the different 

 kinds of shagreen of the shark. It comprehends the cartilaginous 

 fish of Cuvier, with exception of the sturgeon tribe. 



Order II. Ganoides. — This order comprehends families apparent- 

 ly very different from each other, but which, notwithstanding, when 

 minutely examined, have many points of agreement. The character 

 common to them all is the angular form of their scales, which are 

 composed of two substances, one of corneous or bony laminae, super- 

 imposed on each other, and covered with a thick coat of enamel. 

 These scales are constructed precisely like the teeth. In this order 

 are arranged the Lepidoides, Agass., all of which are fossil ; the 

 Sauroides, Agass., fossil, with the exception of two genera, viz. the 

 Lepidostees and the Bichir ; the Pycnodontes, Agass., also fossil ; the 

 Sclerodermes, Gymnodontes, Lophobranches, Goniodontes, SiluridiB, 

 and Sturiones. 



Order III. Ctenoides. — In this order the common character con- 

 sists in their laminated scales being toothed at their posterior edges 

 ■ — those which are externally visible. The teeth of these numerous 

 laminse, which are so placed above each other that the lower always 

 project over the upper, make the scales rough to the touch. This 

 structure is particularly obvious in the Chetodontes and Pleuronecles.. 

 In this order are arranged the Percoides, PoJyacanthes, Scienoides, 



* Recherches sur les Poissons Fossiles, in quarto livraisons ; the plates in 

 folio. The booksellers in London who furnish the work are Black and Arm- 

 strong, 2. Tavistock Street, Covent Garden, and J. B. Bailliere, 219. Regent 

 Street, London. 



