ON THE FOSSIL PHYLLOPODA OF THE PALMOZOIC ROCKS. ane 
_ 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 Herr Dames, ‘that for others, this 
explanation is, according to our present knowledge, inadmissible.’ 
The First and Second Reports drawn up by ourselves! on the Puyt- 
LoropA fully confirm Herr Dames’ own conclusion that all the simple 
dise-like or bivalved shields met with in the older rocks cannot be 
regarded as the opercula of Cephalopods. There are indeed many special 
characters about these Paleozoic 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, Dipterocaris) ; the shape of the shield itself; the 
ornamentation ; and, lastly, the substance composing it. Usually it is 
possible to discern the difference in character between Crustacean and 
- Molluscan structures, as also between these and obscure Ichthyic frag- 
ments. 
We note the following assertion in reference to the body-rings of 
_ Diseinocaris: ‘ Hven if the structures observed are really body-rings, no 
_ stronger proof against their phyllopod nature could 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 recognizable in beds of such 
_ great age.’? (Dames, op. cit.) 
In the presence of the long array of Insect-remains, of the most deli- 
eate 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 durability 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 Ceratiocaris 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,’ Herr 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. 
_ We have long held the opinion that the expanded disc-like shields, 
such as Peltocaris, Discinocaris, Aptychopsis, and some others, were pro- 
_ 1 Also ‘ Geol. Mag.’ 1883, dec. 2. vol. x. pp. 461-464; and 1884, dec. 3, vol. i. 
‘Pp. 348-356. 
_ * Professor 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 which 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 operculwm, but in some Liassic forms the operculum was 
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