Darwin Correspondence Project

New Haven,

Sept. 8, 1856.

My dear Sir:—

I received your most welcome letter a few days before the meeting of our Scientific Association: and as I should meet Prof. Agassiz there, who could best answer your queries respecting the Mammoth Cave Animals, I concluded to defer my answer till my return. Here I am, back again, at last and I seat myself for a few words with you, socially and Scientifically.—

First as to the Mammoth Cave.— Professor Agassiz told me that the family to which the Fishes belong—the Cyprinodonts—was rather strikingly American. With regard to the Insects, Dr John L. LeConte an Excellent Entomologist says that the genera of beetles are not American, but the same that occur in Caverns in Europe & elsewhere. The genus of fly Anthomyia is common in Europe. The Crustacean, Astacus pellucidus, belongs to that subdivision of the genus, (Cambarus, as it has been called), which is peculiarly American. Cambarus is made a distinct genus by some writers: the only difference is in the number of branchiæ: Cambarus has 17 on a side or one less than Astacus.— The Crustacean genus Triura, has not been found any where except at the Mammoth Cave. You may have seen some notice of the species of the Cave in the Amer. Jour. Sci., vol. xi, p. 127 (1851).— Of the spiders I cannot speak definitely.— I would add respecting the genus Cambarus, that its Species are very numerous and widely spread over North America. Agassiz has collected a large amount of information on the peculiarities of the North American Fauna, but he has not yet embodied them in any work or article. One of the most interesting of our peculiar tribes, as you undoubtedly know, is that of the Gar-pikes, of which there are several genera & near two dozen known species occurring over the Continent between Cuba & the northern Lakes—and not represented elsewhere over the globe.— It is not to the point in view, yet I may mention here a fact of geological interest brought out by Agassiz at our Assoc. meeting a fortnight since. There were some young individuals, alive, shown, which had the tail of the Ancient Ganoids— That is, the vertebræ were actually continued to the extremity of the upper lobe— This upper lobe, as here drawn, drops off as the animal grows & the fish then is of the modern type of form. [DIAGRAM HERE]