342 Professor T. Rupert Jones — 



mould of the little form here figured (Fig. 11). The valves are 

 Leperditioid in shape and broadly fabiform. The hinge-line is 

 straight and slopes away with a sudden flattish curve in front and 

 behind (an unfigured specimen has the postero-dorsal slope rounder 

 than that in Fig. 11a). The ventral margin is boldly convex, but 

 sloping or somewhat flattened at its anterior third, thus making the 

 front end of the valve rather sharper, narrower, or more tapering than 

 the posterior. The surface is nearly flat ; but it has a central swell- 

 ing, and a well-marked tubercle at each end, near the middle of the 

 anterior and posterior borders, respectively. In one specimen the 

 hinder tubercle is nearest to the margin, and in another individual the 

 front tubercle is closest to the edge, therefore their relative position 

 was liable to some variation. These specimens are quite unlike the 

 " Beyrichia (? Leperditia) armata, Zeitsch. der d. geol. Gesellsch. 

 XV." [1863, p. 672, pi. 19, figs. 16-18], to which my friend refers 

 them by his label, and which appears to me, judging from the figures, 

 to belong to the genus Arisiozoe, of Barrande. The specimens before 

 me are clearly distinct, and are feature-ful enough to deserve 

 cataloguing under a definite name. I do not know, however, where 

 to place them among known forms except in the genus Primitia ; 

 and the name P. armata will be appropriate, whether the Aristozoe{?) 

 above mentioned was intended for reference or not. With P. armata 

 numerous Tentaculites occur in this Upper-Silurian schist from 

 Thuringia. 



9. Primitia ? cylindrioa (Eichter) ; and another organism. 



Two little pieces of dark-grey Upper-Silurian schist, accompany- 

 ing those above mentioned from Thuringia in 1874, bear some very 

 small, subovate, internal casts, labelled " Beyrichia suhcylindrica, 

 Zeitsch. der d. geol. Gesellsch. xv. and xvii." At first sight these 

 look like granulated and spined valves of some small Cypridiform 

 Entomostracon ; but in one of the specimens the little processes are 

 seen to be cylindrical, and to pass from the convex cast across a 

 narrow intervening space into the surrounding matrix ; and there- 

 fore they must be casts of cylindrical tubes in some investing shell 

 or test, different from that of the Entomostraca. Moreover, both the 

 processes and the granulation caused by their broken bases are too 

 coarse for the ornament of such valves. 



There are also some minute, smooth casts of obscure valves, and 

 many crushed tubes (minute Pteropodaf), on this schist. These 

 smooth valves may belong to Primitia, corresponding with Eichter's 

 smooth variety of his B. cylindrica from the Nereiten-Schiefer (Zeitsch. 

 d. d. geol. G-es. vol. xv. p. 671, pi. 19, figs. 13, 14) ; whilst his 

 prickly variety (I.e. fig. 12, and vol. xvii. p. 365, pi. 10, fig. 7) is, 

 according to my view, a totally different organism. 



10-13. BeyrichijE (Silurian) from Thuringia. Plate X, Figs. 1-6. 



These are casts of Peyrichice from the Upper-Silurian schists of 

 Thuringia, given to me by M. E. Eichter, of Saalfeld, in 1857. 



