APTYCHOPSIS. 97 



difference in character between crustacean and molluscan structures, as also 

 between these and obscure ichthyic fragments. 



We note the following assertion in reference to the body-rings of Discinocaris .- 

 " Even if the structures observed are really body-rings, no stronger proof against 

 their phyllopod nature coi\ld be brought forward, for the body-rings, as well as 

 all the other parts of the Phyllopod (except the shell), are too tender and fragile to 

 remain recognisable in beds of such great age."^ (Dames, op. cit.) 



In the presence of the long array of Insect-remains, of the most delicate and 

 fragile characters, discovered in the Devonian and Carboniferous formations of 

 North America, France, England, and elsewhere, this argument against the 

 possibility of delicate organisms being preserved falls to the ground, whilst the 

 relative thickness and durabihty of the calcareous or chitinous covering of the 

 body-segments in these ancient Crustacea afford no proof for or against their 

 Phyllopod nature, any more than does their relatively greater size when contrasted 

 with existing Entomostraca. Moreover body-rings of Geratiocaris are by no 

 means rare in some Silurian strata. 



3. In the third conclusion, " that even those forms which cannot be referred 

 to Aptychi of Cephalopods are in no case the shields of Phyllopods," Dr. Dames is 

 simply stating a matter of opinion, for of their exact nature and true zoological 

 position Claus himself (to whom he seems to refer) is not at all positive, whilst 

 Dames admits that he has not examined the original specimens.^ 



IX, Genus — Aptychopsis, Barrande, 1872. 



Baeeande, ' Syst. Sil. Boheme,' vol. i, Supplement, 1872, pp. 436 and 455. 



H. WooDwAED, ' Geol. Mag.,' vol. ix, 1872, p. 564. 



H. WooDWAED, ' Eeport Brit. Assoc' for 1872 (1873), p. 323. 



Aemsteons, Yotjng, and Eobeetson, ' Catal. Western-Scottish Fossils,' 1876, p. 7. 



H. WooDWAED, ' Catal. Brit. Foss. Crustac.,' 1877, p. 69. 



Nicholson and Etheeidge, jun., ' Monogr. Sil. Foss. Girvan,' vol. i, 1880, p. 24. 



T. E. Jones, ' Geol. Mag.,' 1883, p. 462. 



T. E. J. and H. W., ' Report Brit. Assoc' for 1883 (1884), p. 216. 



^ Prof. A. von Koenen, replying to Herr Dames on behalf of Mr. J. M. Clarke, very justly 

 observes, "I cannot see that this at all meets the argument, since the relative age of strata is of little 

 influence on the preservation of fossils ; on the other hand, there are plenty of examples in which 

 fossil animals have been furnished with hard, horny, and even calcareous parts vrhich are wanting in 

 their nearest recent analogues. I will only recall here Aptychus and Anaptychus " (' N. Jahrbuch,' 

 &c., 1884, Bd. ii, p. 45). The recent Nautilus has a fleshy hood ; the fossil Ammonite had usually a 

 hard calcareous operculum, but in some Liassic forms the operculum was horny. 



2 See our observations on this subject at pp. 4—8 of Part 1 (1888) of this Monograph. 



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