FKOM NORTH AMERICA, WALES, AND IRELAND. 21 



12. Beyrichia oculieera. Hall. (PI. IV. figs. 19 «, h, 20.) 



Beyrichia oculifera, Hall, ' Twenty-fourth Heport N. Y. State Mns. 

 N. H.' 1871-72, p. 232, pi. viii. figs. 9, 10; Keport ' Geol. Surv. 

 Ohio,' vol. ii. pt. 2, 1875, p. 103, pi. iv. figs. 9, 10. 



Length. Height. Thickness, 



mm. mm. mm. 



o. r Fig. 19 .... 1-9 1-1 -66 (without the boss). 

 ^'^ I 20 ... . 1-7 1-0 



This interesting species is related to B. ciliata, Emmons (B. tumi- 

 frons, Hall), having the two curved parallel furrows and three 

 curved lobes ; but the latter, more uniform and thinner than in B. 

 cilia ta, are not separated one from another ventrally, and the 

 hindermost is developed in the dorsal region into a remarkable pro- 

 cess, like a small thick-stemmed mushroom, smooth (?) on the top *, 

 and delicately beaded round its edge. This is directed backwards, 

 and projects so high, that it is not usually preserved, as it is in 

 fig. 19 a, 6, but worn away, as in fig. 20. This projecting ornament 

 is on the hindermost (highest and thickest) third of the valve, and 

 has no relation to an eye f. 



The valve has a neat, smooth, ventral flange. 



British Museum (no. 59719). Light bluish grey, thin, argillaceous 

 limestone, containing on the bed-planes Ostracoda (B. oculifera 

 chiefly), Polyzoa, Brachiopoda, and fragments of Trilobites, all 

 abundant, and some Encrinital joints. Cincinnati, Ohio. 



IX. IsocreiLiNA, Jones, 1858 ife 1870. 

 1. IsocHiLiNA LiNEATA, sp. nov. (PI. II. figs. bciy b, and 8 a, h.) 



Size 



length. 



Height. 



Thickness. 



mm. 



mm. 



mm. 



104 



•64 



•4 



1-0 



•52 



•48 



Fig. 8 indicates a young individual ; oblong, straight above and 

 below ; ends unc(iually rounded ; surface undulate, steep at the 

 free edges, and particularly abrupt at the ends ; ornamented with 

 very delicate longitudinal strise. 



The adult form in fig. 5 is oblong, with nearly equal rounded 

 ends ; surface gently and almost equably convex, but undulate ; 

 broader and sloping more gently at one end (anterior), and margined 

 with a weak rim or lip on the free edges ; smooth, but faintly lineate 

 near the posterior end. 



This differs from /. Ihieata m its young state (fig. 8) in being 

 larger, convex without abrupt ends, more distinctly lipped, and only 

 feebly striate. 



* In our specimens the facet-like marks figured by Prof. Hall are not visible, 

 and the edge is not fringed but beaded. 



T This fact has already been alhided to in the Ann. & Mag. N. H., April 1886, 

 p. 341. 



