M. Agassiz on the Classification of Fishes. 141 



Placoides, the Cestraciontes^ and the Hyhodontes^ with their 

 subdivisions ; and among the Gano'ides, the Lepiddides, the 

 SaurdideSy the Celacanthes^ and the Pycnodontes^ along with the 

 less important groups, aiid Cephalaspides, Dipteriens, wadLAcan- 

 thodiens. The collateral brinks of the Placoides, which are in 

 general poorly represented in the existing creation, terminate 

 rather early ; the Squalides commence in the coal formation, the 

 Chimeras and the Bays soon after. The Cyclostomes are the 

 only kinds that exist exclusively in our own times. But at 

 the epoch of the chalk, every thing is changed in the class of 

 fishes. All of a sudden we perceive two orders appear, the 

 Ctendides and the Cycldides^ as much diversified from their 

 origin as their predecessors were. Before the commencement 

 of the tertiary period, the Ctenoides comprehend nine dis- 

 tinct families, to which two others must be added during the 

 tertiary epoch, and at the commencement of the present era. 

 The Cycloides are more diversified still ; for after they appear, 

 the type of the Acanthopterygians presents itself by the side 

 of the Malacopterygians, and their numerous families ascend, 

 for the most part, into the era of the chalk. But, notwith- 

 standing these diff'erences, there is a close analogy between 

 the primary representatives of all these types. During this 

 period, the Placoides are reduced, so to speak, to the families 

 of the Chimerae, Sharks, and Rays, and even these are by no 

 means numerous ; while the four new families of the Sclero- 

 dermeSi the Gymnodontes^ the Lophohranches^ and the Aci- 

 penserides, appear almost at the same time in the family of 

 the Ganoides, replacing those which become extinct. The 

 lists of fossil fishes, arranged according to geological forma- 

 tions, which will be found in my work, will render these ge- 

 neralities more consistent, while they will serve, at the same 

 time, as direct proofs of them. 



Such facts as these loudly proclaim principles which science 

 has not yet discussed, but which paleontological researches 

 bring under the notice of the observer, with a continually in- 

 creasing force, I refer to the relations which the creation 

 bears to its Creator. Phenomena closely allied in the order 

 of their succession, and yet without sufficient cause in them- 

 selves for their appearance; an infinite diversity of species 

 without a common material bond of connection, grouping^ 



