330 BRITISH SILURIAN BRACHIOPODA. 



In Ireland it has been met with at Doonquin and Ferriter's Cove, Dingle, County 

 Keirv. 



Lept^.na (vel Chonetes ?) tenuissime-striata, M'Coy (sp.). PI. XLIX, figs. 20 — 2:2. 



Orthis tenuissime-striata, M'Coy. Sil. ro.«s. Ireland, pi. iii, fig. 20, 1846. 

 Lept^na — (?) Id. Biit, Pal. Foss., p. 239, pi. i h, fig. 44, 1852. 



— — D'Eichwald. Lethsea Rossica, vol. i, p. 8/1, 18;i9. 



Sj)ec. Char. " Semicircular ; twice as wide as long ; both valves flat ; hinge as 

 long as the shell is wide ; cardinal angles slightly pointed ; cardinal area narrow, with 

 nearly parallel sides ; striation of the surface scarcely visible to the naked eye, composed 

 of extremely fine, equal, radiating strise, slightly branching " (M'Coy). 

 Length 6, width 12 lines. 



Obs. I know very little about this obscure so-called species, and consequently 

 reproduce Prof. M'Coy's original description, as I am not certain that his second 

 description and figures (p. 239, 'British Pal. Fossils') apply to the same species; and 

 evidently he is not himself certain as to what his shell really is. In the last-named 

 work the author observes that in form it strikingly resembles the Leptcena {Chonetes) lata 

 of the Ludlow rocks ; but is destitute of spines on the hinge-line, and is easily dis- 

 tinguished by the much greater fineness of the striae, or the greater number in a given 

 space ; and that when the larger strise can be distinctly seen, which is not often the case, 

 the resemblance is very strong to Leptcsna sericea^ from which it differs in the flatter 

 entering (dorsal) valve, in the finer and more equal strise, without the larger striae, and 

 in the distinct, radiating, coarsely punctured lines of the interior, and the small size 

 of the bilobed muscular impressions of the receiving (ventral) valve, in the form of which, 

 however, there is some resemblance. I obtained from Sir R. Griffith the loan of Prof. 

 M'Coy's original example (fig. 22). It looks like a Chonetes, and may possibly belong 

 to that genus ; but it is a crushed flattened impression, and I would by no means 

 venture to express any decided opinion as to its specific value. I have reproduced Prof. 

 M'Coy's description and figures, in the hope that better examples may be sought for in 

 the original locality. Mr. Salter unites this species with Orthis protensa (' Mem. Geol. 

 Surv.,' vol. ii, p. 289) ; but Prof. M'Coy objects to the identification on the grounds that 

 the latter has vastly coarser and fasciculated strise. 



Position and Locality. Abundant in the Caradoc (?), slates of Slieve Roe, 

 Rathdrum, County Wicklow, Ireland. In his work on ' British Pal. Foss.' Prof. M'Coy 

 states that this shell occurs in several Welsh localities (Caradoc), such as Moel, Saesiog, 

 Llanrwst, Denbighshire ; the Bala Limestone of Llandeilo, Caermarthenshire, &c. ; but, 



