Palceozoic Bivaloed Entomostraca. 407 



border is straight in this instance, as in PI. XII. fig. 1, and 

 not curved as in figs. 2-8. 



Three (Vine Coll. XXXVil, (fig. 12). Bed no. 37, 

 < BuildwasBeds. 



specimens :| ^^^^^^ BuildwasBeds. 



4. Octonaria^j sp. 

 Proportions :— L. 21. H. 12i Th. 8. 



There was also a unique and peculiar specimen from the 

 Tickwood Beds, but unfortunately lost, which presented an 

 ovate convex valve, having a large, well-defined, oval, central 

 depression, with a small tubercle rising in its middle. The 

 broad raised part of the valve surrounding the hollow may be 

 equivalent to the narrower ridge in Octonaria octoformis and 

 its varieties, and the central pimple might find its analogue in 

 the isolated tubercle in figs. 8 a, h. The valve in edge view 

 ■was flattened along the middle and steeply sloping at the 

 ends, as in Octonarice. Seen on the inside the valve showed 

 marks of a hinge-line on one margin free of matrix. 



In his paper on the Cambrian and Silurian fossils of West 

 Gothland (' Kongl. Svenska Yetenskaps-Akad. Handl.' 

 vol. viii,, 1869) Dr. J. G. O. Linnarsson described and figured 

 two small Ostracodes which apparently have some relationship 

 with the form described above as a doubtful member of the 

 Octonarian group. Thus at p. 85, pi. ii. fig. 68, one of the 

 illustrations of his Beyrichia costata (from the Beyricliia- 

 limestone) has an isolated tubercle, rather forward (?) on the 

 valve, within a circular ridge and furrow. His figure of 

 Primitia strangulata (fig. 69, from the same limestone) appears 

 to be not Salter's species, but a simple convex suboblong valve 

 with a sunken tubercle on it, very much like the above-men- 

 tioned dubious Octonarian form. 



To the same category we may perhaps refer Dr. E. Rich- 

 ter's figs. 13 and 14 in the pi. xix. illustrating his paper on the 

 schistose rocks of Thuringia (Zeitschr. d. d. geol. Ges. vol. xv., 

 1863). These two figures show small, suboblong, obscure 

 valves, each having a central tubercle ; and, with others, 

 Kichter referred them to his Beyrichia suhcylindrica, from the 

 Nereites-bed, p. 671. See also Geol. Mag. 1881, p. 342. 



III. BoLLiA, Jones & Holl, 1886. 

 Bollia, Jones & Holl, Ann. & Mag. Nat. Hist. ser. 5, vol. xvii. p. 3G0. 



This genus, related to Beyrichia, but distinguished by having 

 one median sulcus and two lobes, was established for B. hicol- 



