96 BRITISH PALAEOZOIC PHYLLOCARIDA. 



America, and described by M'Coy, Salter, Barrande, Meek, Hall, Clarke, our- 

 selves, and others, after an elaborate criticism of the subject. Dr. W. Dames 

 concludes : 



1. That some of the bodies in question are the Ajptycld of Goniatites. 



2. That for others this explanation is, according to our present knowledge, 

 inadmissible. 



3. That the last are, however, in no case Phyllopods. 



1. As intimated above, we accept the first conclusion. The British Museum 

 has obtained several specimens of these Aptychus-like bodies^ from the black 

 limestone of Bicken ; and Mr. Robert Etheridge, jun., discovered among them a 

 specimen of a small Goniatites Intumescens with an imperfect Aptyclms in situ 

 in its mouth-aperture. This Aptyclms seems to agree most nearly in form with 

 the so-called CanJiocaris lata from Budesheim in the Bifel,'* also observed by 

 Mr. J. M. Clarke at Bicken.^ The other specimens of Aptychus-like bodies, not 

 in sitii, but from the same black Devonian limestone, agree very closely with 

 Mr. Clarke's SjMthiocaris Koeneni* also from Bicken. 



2. Even after all those forms of supposed Phyllopod shields which occur in 

 beds in which Goniatites have been found shall have been re-examined, we feel 

 convinced, with Dr. Dames, " that for others this explanation is, according to our 

 present knowledge, inadmissable." 



The first and second reports drawn up by ourselves' on the Phyllopoda (Brit. 

 Assoc.) fully confirm Dr. Dames' own conclusion that all the simple disc-like or 

 bivalved shells met with in the older rocks cannot be regarded as the opercula of 

 Cephalopods. There are, indeed, many special characters about these PalfBOZoic 

 Phyllopod shields that will require to be carefully examined before they can all 

 be referred to Goniatites. We would draw attention to the varied form of the 

 notch, the absence in some and the presence in others of the dorsal suture ; the 

 presence in different genera of the rostral portion of the shield in the circular and 

 oval forms, and the possible existence in some of a hinder trigonal shield-piece 

 {Pholadocaris, Dijderocaris) ; the shape of the shield itself; the ornamentation; 

 and, lastly, the substance composing it. Usually it is possible to discern the 



1 "We have also seen a specimen of Aptyckus sent to Mr. John Edward Lee, of Torquay, by 

 Prof. Ferd. Romer, of Breslau, and labelled " Aptychopsis, sp. = operculum of Goniatites intu- 

 mescens, Upper Devonian, Bicken, near Herborn, Nassau," in Dr. Eomer's own handwriting. Some 

 of these specimens have been figured in the ' Geol. Mag.,' dec. 3, vol. ii, pi. ix, figs. 1 — 6, in illustra- 

 tion of a paper (pp. 345 — 352) treating of this subject in full, and of the relationship of the fossil 

 Phyllopods under notice to Nebalia. 



2 See ' Geol. Mag.,' 1882, dec. 2, vol. is, p. 388, pi. ix, fig. 13. 



3 ' Neues Jahrb.,' &c., 1884, vol. i, p. 181, pi. iv, fig. 2. 

 * Ibid., fig. 1. 



6 Also ' G-eol. Mag.,' 1883, dec. 2, vol. x, pp. 461^64 ; and 1884, dec. 3, vol. i, pp. 348—356. 



