88 EEroRT— 1884. 



Woodward. 1 Thus an angular notch is often present in the forepart of 

 the fossil carapace. The median suture has often been pressed inwards, 

 but more frequently it has parted, leaving the two larger parts of the test 

 separate. These remain as subtriangular plates, straight-edged but 

 angular on the inner margin, and either elliptically curved or almost 

 semicircular on the outer or free borders. They occur usually as black 

 carbonaceous films on the bed-planes of the strata ; but sometimes they 

 have a somewhat corneous or chitinous appearance. 



A concentric linear ornament covers the whole shield ; numerous 

 delicate ridges and furrows, following the curve of the outer margin, 

 converge and are concentric at the point where the dorsal and nuchal 

 sutures meet, at or in front of the centre of the test. The style of orna- 

 ment is similar to that of the bivalve Estheria, which shows a neat 

 arrangement of raised lines of growth, concentric with the umbones. 

 In the case of Elli-psocaris, even the interlinear sculpturing is present. 

 (' Geol. Mag.' Oct. 1862, p. 4i5.) If the two valves of Estheria be laid 

 open, their surface would represent the shield of Aptycltopsis ; the open 

 angle then formed by their anterior margins would be analogous to the 

 nuchal notch ; and for that of their hinder margins we may find an 

 analogue in the split posterior border of Dipterocaris and other forms 

 allied to Discinocaris and Aptychop>si$. 



1. Aptychopsis prima, Barrande, 1872, and var. Secunda. ' Parallcle 

 entre la Boheme et la Scandinavie,' 1856, p. 62. ' Svst. Sil. 

 Boheme,' vol. i. Suppl. 1872, p. 457, t. 33, figs. 1-21. Roemer, 

 'Leth. Geogn.' 1876, t. 19, f. 3a, Zb (after Barrande). 



This includes, according to M. Barrande, both round and somewhat 

 obovate forms of the tripartite shield-like test, which both Barrande and 

 H. Woodward termed Aptychojms independently in the same year (1872). 



Among the figures on plate 33 of Syst. Sil. Boheme,' vol. i. Supplem. 

 circular forms are represented by figs. 1-8, 12-18, 20, and 21 ; and more 

 or less obovate tests by figs 9-11 and 19. 



In the British Museum (Natural History) are some specimens labelled 

 by M. Barrande many years ago, as ' Aptychus ? primus ' and ' Aptychus ? 

 secundus.'' The former were decidedly obovate forms, when perfect, with 

 the two lateral moieties and the frontal (cephalic or rostral) in place ; and 

 the latter (when perfect) were nearly or quite round. Evidently our 

 deceased friend had decided to group the two kinds together, by the time 

 he published the Supplemental volume of his great work treating of these 

 Phyllopods. The circular shields found in Bohemia are chiefly from the 

 schistose or slaty mudstone of Borek, with some from Litohlow and 

 Kozel — all in Etage 'Eel'; and the ovate or obovate forms come from 

 the same geological origin, but in limestone at other localities, as 

 Butowitz, Slawick, and Wohrada, and rare at Kozel. 



We think that it will be advisable to distinguish the two forms, by 

 regarding one of them as varietal. Keeping M. Barrande's specific term 

 Aptycliopsis prima, because his extensive series of specimens gave him 

 reason to regard the majority as being rather longer in the fore and aft 

 diameter than in the transverse direction, and therefore not essentially 

 circular, we may look upon the elongate and decidedly obovate forms as 



1 Quart, Jour. Geol. Soc. vol. xxii. p. 504 ; and Geol. Mag. Dec. 2, vol. is. p. 387. 



