ON THE FOSSIL PIIYLLOPODA OF THE PALAEOZOIC ROCKS. 77 



centric lines of growth, and, in some cases, in the delicate surface orna- 

 ment between them. 



Another objection to the supposed Aptychus nature of many of these 

 circular and ovate shields arises from the fact that they were not origi- 

 nally flat discs or plates, as may be seen by examining a series from 

 various localities. 



Thus Discinocaris Broivniana was in some degree convex, with a 

 low conical apex ; Aspidocaris triasica was evidently conical, as may 

 be seen by the split state of the outer rim, caused by the flatten- 

 ing of the whole shield ; others, as Spathiocaris Emcrsonii and 

 Lisgocaris Lutheri, had elevated subconical carapaces. Aptychopsis not 

 unfrequently exemplifies the same condition and similar breakage. A 

 median mark, caused by the depression of the central portion in 

 Cardiocaris bipartite/, and 0. Koeneni, is also the result of flattening in a 

 toughish subconical shield. Again, some of these carapaces were bent 

 like a low ridge along the dorsum, as shown by Mr. J. M. Clarke's de- 

 scription and tigure of Dipterocaris procne— all which conditions are com- 

 patible with the nature of Phyllopods. 



Phyllopodoiis Shields figured by early observers (1832-1850). 



1. 1832—48. — One of the above-mentioned little fossils has been re- 

 corded as ' Aptychus Icvvigatus (Goldfuss) ' in von Dechen's Gorman 

 translation of De la Beche's ' Manual of Geology,' ' Handbuch der 

 Geognosie,' 1832, p. 529 ; and it was entered in Bronn's ' Index 

 Palaeontologicus,' 1848, vol. i. p. 90. As we know of no figure, we cannot 

 offer an opinion as to its generic relationship. 



2. 1842. — The ' Aptychus vetustus ' of d'Archiac and de Verneuil, 

 ' Transactions Geol. Soc. London,' ser. 2, vol. vi. 1842, p. 343, pi. 26, f. 

 9, found in the Devonian beds of the Eifel (rare), is one of these little 

 apparently bivalved but really tripartite carapaces, with a front notch, 

 and an open split at tlie hinder part of the median suture. If this latter 

 feature be an original condition, as it seems, the species is referable to 

 Dipterocaris. 



3. 1846.- — In 1846 A. von Keyserling gave figures and descriptions of 

 some small Aptychus-like fossils in the ' Wissenchaft. Beobacht. Pets- 

 chora-Land, Geogn. Beobacht.' p. 286, pi. 13, f. 3-7. These he referred 

 to as being probably the Aptychi of Goniatites. The figures show no median 

 line of suture ; and therefore, instead of looking like the more common 

 Aptychopsis, they resemble the allied Discinocaris, with an undivided shield, 

 and with a rounded or elliptical nuchal or cephalic notch. If this latter 

 feature be real, we have a form here which comes near Ellipsocaris. One of 

 his figures in particular (fig. 3) reminds us of this genus. 1 



4. 1850.— In the ' Palseontographica,' vol. iii. p. 28, pi. 4, fig. 18, 

 F. A. Roemer described and figured his Aptychus dubius, from the Upper 

 Devonian beds of the Hartz (Goniatite-limestone of the Kelwasserthal). 

 M. Barrande in 1872 was inclined to refer it to Aptychopsis (' Syst, Sil. 

 Boheme,' vol. i. Suppl. p. 456) ; Mr. J. M. Clarke thought it might be a 

 Spathiocaris ; but we regard it as a Discinocaris. 



5. 1850. — In the same volume of the ' Palasontographica, ' iii. p. 88, 

 t. 13, f. 13, P. A. Romer also illustrated what he regarded as an Aptychus 



1 We are informed that unfortunately these Kussian specimens cannot now bo 

 found at St. Petersburg-. 



