ON THE FOSSIL PIIYLLOrODA OF TI1E PALAEOZOIC ROCKS. 87 



cuds. The edge-view of (lie cast is like a half-opened bivalve carapace, 

 with a definite strong anterior notch and a small weak posterior indenta- 

 tion between the ends of the valves. 



Cytheropsis is not a good generic term ; but we cannot offer any 

 additional information on this peculiar form. 



Zonozoe complexa and Z. Braboivensis (op. cit. p. 554, &c.) may 

 possibly prove to be symmetrical opercula of some shells. 



M. Barrande's Cryptoearis ( op. cit. pp. 459, &c.) was placed by him 

 next to Aptychopsis with considerable doubt. We incline to the belief 

 that most of the examples of this little form correspond with opercula of 

 Gasteropods, and thns are comparable with such fossils as Peltarion, 

 which is now known to be the opercule of a N&ritopsis, We may suggest 

 also that some of the forms referred to Cryptoearis have a distant like- 

 ness to the opercula of such Corals as GfoniophyUwrn, &c. 



IX. Crescextilla, Barrande, 1S72. Crescentillapugnax,Ji9,Tr. ' Syst. Sil. 



Boheme,' vol. i. Supplem. p. 507, pi. 26, figs. la-i. 



Placed among the doubtful Entomostracan forms by our late friend 

 Barrande, this curious little fossil seems to us to fall into its natural 

 grouping near Pterocaris and Dipterocaris, for it is open behind, and, 

 though found in separate pai-ts, it was also found with sides united, and 

 it may have been sutured along the very short line of junction which the 

 shape of its laterals allowed. 



If we look at M. Barrande's fig. 1 b in a position reversed (upside 

 down) to that in which it is di*awn, we shall readily observe that the two 

 reniform lateral pieces, meeting at their convex borders, have the charac- 

 teristic triangular cephalic piece at one end, and an open notch at the 

 other, just as in Pterocaris. The shape, however, of the nearly semi- 

 circular or short-reniform laterals, with their outside crescent points, 

 makes them markedly distinct. The test, apparently smooth, and faintly 

 convex, has been replaced by iron-oxide. It is minute, being only a little 

 more than 1 mm. in fore and aft measurement, by about 2 mm. across. 

 Specimens were found in Etage d ; some in d 2, near Trubsko ; most in 

 d 3, near Trubin : a few in d 4, near Chrustenitz, and d 5, near Koenigshof . 



' Thus,' says M. Barrande, ' this species ranges nearly throughout the 

 Quartzites D, c to d of the Faune seconde.' 



X. Aptychopsis, Barrande, 1872. ' Syst. Sil. Boheme,' vol. i. Suppl. 



pp. 436, 455 ; and H. Woodward, 1872, ' Greol. Mag.' vol. ix. 

 p. 564 ; « Report Brit. Assoc, for 1872, 1873,' p. 323. 



A circular or elliptical, slightly convex, tripartite shield or carapace ; 

 divided by a median ' dorsal ' suture extending from the posterior margin 

 forward to within half, or a third, or a fifth, of the length of the test, accord- 

 ing to the shape of the latter, and then meeting the apex of a symmetrical 

 V-shaped suture, which extends to the front margin at different angles in 

 different species. This angular (' nuchal ') suture forms a line of much 

 weaker resistance than the longitudinal suture ; and the carapace has 

 very frequently given way after the death of the animal, and allowed the 

 triangular (' rostral ' or ' cephalic ') portion to be removed, together with 

 the anterior limbs and soft parts of the animal, as suggested by Dr. H. 



