FEOM NOETH AMERICA, WALES, AND IllELAND. 9 



specimens figured in PI. IV. figs. 8-] 3, appear to be Primitia uni- 

 cornis (Ulricli), 'Journ. Cinciun. Soc. N. H,' vol. ii. 1879, p. 10, 

 pi. vii. fig. 4. 



" Leperditia cyUndrica, Hall," is mentioned by H. IVI. Ami as 

 occurring, Avith Beyrichia ocidifera, in the Siphonotreta-limestone 

 (' Ottawa Naturalist,' December 1887, p. 3 of separate copy) ; also 

 by C. D. Walcott (' Albany Instit. Trans.' 1879, pp. 23 & 37 of 

 separate copy), with B. ocuUfera and B. cincinnatensis, in the " Utica 

 Slate" of Oneida Co., N. Y. 



Small casts of a similar species occur in the hard black shale 

 (" Utica Slate") of Ottawa, with Trilobites, Encrinital joints, &c. 



8. Primitia AYhitfieldi, sp. nov. (PI. III. figs, 24 a, 24 b.) 



Size : length -8 mm., height '33 mm. 



Elongate-oblong, convex, with a wide shallow dorsal depression ; 

 ends rounded unequally, the posterior having a cardinal angle, 

 whilst the anterior end is neatly rounded. The surface is orna- 

 mented with a very delicate reticulation of long, oblique, minute 

 meshes (fig. 24 b). 



This specimen is in the British Museum, marked 59723, from 

 Cincinnati, Ohio. It is in a thin piece of grey limestone, split off a 

 mass along the bedding ; made up of small organisms, shaly on one 

 face, and rusty at the edge. On it are " Leperditia cyUndrica, Hall," 

 very abundant, with Leperditia ? minutissima^ Primitia Whitfieldi^ 

 and Beyrichia BucJiiana ? (fig. 25). The last two are very rare ; 

 I lie Beyrichia is in the cast of a small ripple-mark on the bed-plane. 



II. Genus Piumitiopsis, Jones, 1887. 



Primitiopsis, Jones, ' Silur. Ostrac. Gothland,' 1887, p. 5 ; and 

 ' Ann. & Mag. Nat. Hist.' ser. 6, vol. ii. 1888, p. 406. 



1. PETMiTiorsis pukctulieera (Hall). (PI. II. figs. 7 a, b; 12 «, b ; 

 13 a, b.) 

 Leperditia jnmctulif era, JLnl], ^Thirteenth. Annual Report of the 

 Regents of the University of New York,' 18()0, p. 92. 



Length. Height. Thickness *. 



mm. mm, mm. 



Pig. 7.... 1-08 -G -48 



Size^ 12 1-35 -84 -8 



13 1-48 -84 -8 



Figs. 7 a, b, fairly correspond with Dr. James Hall's description 

 referred to above, but there are more than one little tubercle on the 

 valve, and the ventral margin is not so distinctly thickened. 

 (Pig. 7 a has had its postero-dorsal edge partly broken away.) 



Taking fig. 7 as a young form, and figs. 12 and 13 as adults, we 

 find in the latter a subovate carapace, full in the middle, contracted 

 at the ends, not quite equally : and more strongly compressed in 



* " Thickness " refers throughout to the thickness of liie carapace (closed 

 valves). 



