350 Prof. T. H. Jones — On some Palceozoic PhyUopoda. 



12. PiNNOCARis, E. Etlieridge, jun., 1878. Possibly bivalved, and without 

 rostral piece. 



1. Lapivorthi, R. E., jr Shield triangular-obovate (if the two 



lateral pieces be laid out together). 



It is well known that some of these Phyllopodous tests, shields, or 

 carapaces were noticed and figured by early observers ; and, from 

 their general resemblance to the Aptychus of Ammonites, they were 

 thought to be Aptychi of Goniatites. Such are — 1. Aptychus Icevi- 

 gatus (Goldfuss), in Von Dechen's " Handbuch der Geognosie," 1832, 

 p. 529 (not figured and undetermined). 2. The Aptychus vetustus, of 

 Vicomte d'Archiac and E, de Verneuil, Trans. Geol. Soc. London, 

 ser. 2, vol. vi. 1842, p. 343, pi. 26, fig. 9, from the Devonian rocks 

 of the Eifel : this appears to be such a form as is now referred to 

 Dipterocaris. 3. Count Alexander von Keyserling in 1846 figured 

 and described some small Aptychus-like fossils in the " Wissensch. 

 Beobacht. Petschora-Land," p. 286, pi. 13, figs. 3-7. These were 

 found in Devonian strata, and he regarded them as the opercula or 

 Aptychi of Goniatites ; but their contours do not quite match the 

 shape of the apertures of these shells, although some of the outlines 

 given on the plates are nearly coincident. They approach closely 

 the Phyllopod shields known as ElUpsocaris. 4. In 1850 F. A. 

 Eoemer described and figured his Aptychus diibius, from the Upper 

 Devonian beds of the Hartz, nainely, from the Goniatite-limestone of 

 the Kelwasserthal, " PalEeontographica," vol. iii. p. 28, pi. 4, fig. 18. 

 Mr. J, M. Clarke has referred it to Spathiocarts, but it seems rather 

 to be a Discinocaris. 5. In the same volume, p. 88, pi. 13, fig. 13, 

 F. A. Koemer gave also another such fossil as an Aptychus, from the 

 Goniatite-limestone of Altenau, Hartz. The figure suggests that it 

 might be a Pholadocaris. 



It has been argued that only some of these small, black, carbona- 

 ceous, filmy, shield-like bodies can have belonged to Phyllopods, 

 and that many of them were really opercula or Aptychi of Goniatites.^ 

 It appears to us, however, that the little fossils under consideration 

 resolve themselves into certain categories. Thus, for example, we 

 have forms like Discinocaris, which could not, by reason of their 

 shape in general, and the presence of their frontal piece in particular, 

 have belonged to any Cephalopod, much less to a Goniatite, even if 

 it possessed an operculum, which is by no means proved. Next a 

 lai'ge series of forms occur in strata wherein no Goniatites have been 

 found. As to such as have been met with in beds containing 

 Goniatites, as in Nassau, the Eifel, the Hartz, and Petschora-Land, 

 it is to be remarked that their outlines do not correspond exactly 

 with the apertures of the shells of such Cephalopods. As other 

 Phyllopods (such as Estheria) are imbedded in Devonian rocks, it is 

 not strange that these Phyllocaridas should be there present. Whilst, 

 however, we do not deny that some forms now associated with un- 

 doubted shield-bearing Phyllopods may hereafter be shown to be 

 Molluscan, where there is any possibility of doubt the onus pro- 

 hancli must rest with those who are dissatisfied with our views 

 regarding their affinities. 



1 See Herr Dames, N. Jahrb. i. Min. etc., 1884, i. p. 275, etc. 



