404 Prof. T. R. Jones on the 



March 1887, p. 194). Indeed it has been figured and de- 

 scribed from that source, under the name of Primitia minuta, 

 by Dr. A. Krause, in the Zeitschr. d. d. geol. Ges. vol. xxix. 

 p. 38, pi. i. fig. 19. 



o C Vine Coll. no. LXVo. Shales over Wenlock 



S?^^^ i Limestone. 



{ 



specimens : J ^^^^^^ ^^ Tickwood Beds. 



cj r Smith Coll. no. 4. Eailway-cutting,sideof 



^^^®" \ Severn, Ironbridge. 



specm:ens:| ^^ Woolhope. 



II. OCTONARIA, gen. nov. 



In this peculiar form of carapace the valves are subovate in 

 outline, thick, and flattened, with variously moulded surface. 

 The ventral margin is usually straighter than the dorsal. 

 The superficial plateau is more or less regularly bordered 

 by a curved ridge, within which there are one or more hol- 

 lows and diiferent elevations ; the latter are usually connected 

 with the ridge, but sometimes isolated. The inclination 

 shown by the ridge in many cases to turn in on itself in the 

 ventral region, and thus more or less closely imitate a. figure- 

 of-eight^ is the foundation for the generic name. In all 

 cases the edge view of the carapace is much like that of Thlip- 

 sura corpuhnta^ that is, suboblong with subacute ends ; the 

 valves being nearly flat on the surface and sloping down to 

 the edges all round, like a high pie in a deep dish, and like 

 some metal cover-dishes used for entrees &c. 



1. Octonaria octoformis, sp. nov. 

 (PI. XII. figs. 2 a, 6 ; and varieties figs. 3 a-8 h.) 



Proportions :— L. 27. H. 15. Th. 13. 



In this form the surface-ridge is slightly bent inwards on 

 the dorsal region, and turned in with a loop ventrally, thus 

 meeting mcsially and forming a figure-of-eight. This, for 

 convenience, is taken as tlie type. 



One specimen : — Vine Coll. no. XVIII2. Bed no. 25*. Tick- 

 wood Beds. 



1*. Var. intorta^ nov. (PI. XII. figs. 3 a, 3 Z-.) 



Proportions .—L. 23. H. 13. Th. 11|. 



The ridge is perfect dorsally in this case^ but divides below, 

 and turns in its two ends, one of which (anterior) is thickened. 

 One specimen : — Smith Coll. no. 80. V\^oolhope. 



