62 Prof. T. R. Jones on the 



further across the valve. It is not very diflferent from 

 P. nitida^ fig-s. 1 and 2 of the accompanying Plate. 



This specimen occurs (with Spirigerina reticularis ?) in a 

 dark grey, fine-grained, Lower-Devonian sandstone, belonging 

 to the Spirifer-Sandstone of OiFdillen, h\ the north part of the 

 Dillenburg District, Nassau. It is tiie form referred to as 

 Primitia sacculus by Prof. F. von Sandberger in the 

 ' Jahrbiich. Nassau. Naturk.,' Heft 42, 1889, pp. 33, 34, 37, 

 38 ; and from Prof. v. Sandberger's information 1 gather 

 that a similar form occurs in the Lower Devonian at Stadtfeld, 

 in the Eifel. 



There are other Primitian forms in this hand-specimen, 

 rather obscure, but longer and more reniform than fig. 7 ; and 

 Beyrichia striciisulcata^ fig. 11, is present in some abundance. 



3. Primitia nitida (F. A. Roemer). 

 (PI. VTL figs, la, h, 2a, b.) 



Suboblong, rounded at the ends, boldly curved on the ventral 

 and nearly straight on the dorsal border; surface convex, 

 more so behind than before, black and shining, but minutely 

 pitted with a delicate reticulation, sucli as is seen on P. mua- 

 dula (Ann. & Mag. Nat. Hist. 1889, iii. pi. xvi. figs. 2 a and 

 6 a), and much smaller than fig. 4c of the present Plate. It 

 bears also the usual sulcus, more exactly mid-dorsal (fig. 2 a) 

 than in P. mundida, and reaching to the centre of the valve, 

 where it slightly expands (fig. la), and in a larger (older?) 

 shell it has contracted in its middle and left around j)it where 

 it terminated (fig. 2a). These features are liable to much 

 modification, and Roemer's representation of the little tubercle 

 and pit at tiie end of the furrow may be sufficiently accurate, 

 as, indeed, is his general description. 



P. nitida has nearly the shape of P. mundida (Ann. & Mag. 

 Nat. Hist., Sept. 1855, pi. vi. fig. 29 a), but has a more reni- 

 form outline, longer sulcus, and apparently no marginal rim. 



The two specimens here figured occur with several others 

 in a piece of black limestone (with Pterinea ventricosa, 

 Goklfuss, and Cardiola retrostriata^ Buch), belonging to the 

 Upper- Devonian Goniatiten-Kalk, at Altenau, in the Harz. 

 It was sent by F. A. Roemer to Fr. von Sandberger, but 

 does not seem to contain the specimen figured by Roemer. 



