388 



DR F. A. BATHER. 



§ 110. Horizon. — Very rare in d3, the black micaceous shales of Trubin, which are 

 only a local facies of d4, rich in Trinucleus ornatus but with no characteristic fossils. 

 Barrande assigns to Trubin the originals of his pi. 27, ff. 1, 17, and 18 ; but Dr Perner 

 says that the last is the only specimen unquestionably of that provenance. Very 

 common in d4, the micaceous shales of the neighbourhood of Zahorzan, which in time 

 approximately correspond to the passage from Llandeilian to Caradocian. 



§ 111. Material. — For reasons previously given (§§41, 92), of the specimens definitely 

 mentioned by Barrande only those from Zahorzan can be regarded as syntypes. But 

 to save future confusion 1 select as Lectoholotype the original of Barrande, pi. 26. 

 ff. 6, 7, represented in the British Museum by squeeze E 16005 (our PL I. fig. 5); the 

 remaining syntypes thus become paratypes. Scarcely inferior in systematic value is 

 Brit. Mus. E16031 (PL I. fig. 6), received from Barrande with his label "Cystid. 

 Sedgwicki Barr. D — Zahorzan." E 1 60 18-E 16021 were specially obtained for this 

 memoir from the R. Bohemian Museum (PL I. figs. 7, 8, 9). That museum has also 

 enabled me to study the Trubin specimen (§ 110), squeeze E 16007. 



§ 112. Description. — (Text-fig. 8.) Theca. Outline, owing to crushing, not so 

 clear as in D. Barrandei, but certainly cordiform rather than "ovoid" (Barrande) 

 or " beutelformig " (Jaekel). Lobes apparently do not project much below stem- 

 attachment. Narrow end truncated somewhat squarely, with one angle supporting 

 the brachiole and the other simply rounded off, as shown in Barrande, pi. 26, fi". 1, 

 12, and the original of if. 6, 7. In the last specimen the lobe on the adbrachial side 

 seems to be the larger (cf. our PL I. figs. Q,7) \ but no rule can be laid down. In 

 E16031 (PL I. fig. 6) the tract occupied by the umbonate plates (§§ 52, 115) is convex, 

 but usually it has been flattened out. 



S 113. Measurements of Theca in millimetres : — 





Height. 



Width Above. 



Greatest Width. 



Ratio of Width 

 to Height. 



Holotype 

 E 16031 

 E 16019 

 E 16021 



37 

 35-5 

 ca. 31 

 ca. 27 



21 

 ca. 13-5 

 ca. 15 

 9 



37-5 



32-5 

 ca. 31 

 25-5 



101 

 •91 



1 

 •94 



Probably the relative width is exaggerated by crushing, but it is not likely to have 



been less than "9. 



§114. Thecal Plates. — -Diameters observed in the ordinary plates, including 



umbonate plates : — 



Holotype ..... "6 mm. to 41 ram. 



E 16021 ...... 1-6 mm. to 3-7 mm. 



E 16031 1-3 mm. to 4 mm. 



The sizes are mixed quite irregularly ; but it is not unusual for a large plate to be 

 surrounded by small ones (cf. Eocystis longidactylus, Deutocystis modesta). 

 Thickness of the ordinary flat plates not over '5 mm. 



