STROPHOMENIDiE. 325 



In Scotland it occurs in the Caradoc Limestone of Craig-liead, near Girvan, in 

 Ayrshire, and in several other localities in the same district. 



In Ireland it abounds in many places, such as Grangegeeth, County Meath ; Bally- 

 geale, Waterford ; at Portraine, at Kelly Pomeroy, Desertcreat, &c. 



Abroad it has been found in Russia, Esthonia, Bohemia, Norway, Spain, the Island 

 of Anticosti, Canada West, the United States, &c. 



Var. a— RHOMBicA, M' Coy . PI. XLVIII, figs. 20—22. 



Lept^na sericea, var. rhombica, M-Coy. Brit. Pal. Fossils, p. 239, 1852. 



" In this variety the shell is more gibbous in the middle than in the true types, and 

 less transverse ; the proportional length varying from j^ to i^, as compared with the 

 width ; and the strong ridges fewer and often nearly a line apart, sometimes elevated on 

 obtuse folds near the margin ; in those respects approaching the L. transversalis, from 

 which, however, it differs in having the intervening strias of the same size and strength 

 as the ordinary types ; wanting the remarkable large punctures on the interior, &c. ; the 

 muscular impressions also agree rather with L. sericea than with the L. transversalis." — 

 M'Coy. 



Obs. I have reproduced Prof. M'Coy's reasons for making this a variety of L. sericea. 

 I know nothing of its interior ; and the chief difference I can perceive rests on the 

 greater size of the shell, some examples having attained — 



Length 11, width 17 lines, 

 much larger proportions than given to L. sericea. 



This form will require further study, especially as to its interior. 



Position and Locality. This variety occurs in the Caradoc-Bala at Moclydd, near 

 Oswestry ; Pwll-y-wrach-isaf, Llanfyllin ; Alt-yr- Anker, Meifod ; Mathyrafal, south of 

 Meifod ; Pen-y-Craig, Llangynyw, Montgomeryshire. Belli Grin, Bala, Merionethshire. 

 Glyn Ceiriog, Denbighshire, &c. 



In Scotland it has been found at Craig-head Quarry, near Girvan, in Ayrshire. 



Lept^na scissa, Salter. PI. XLVII, figs. 21 — 25. 



Lept^Ka scissa, Salter, MS. Catal. Coll. Foss. Mus. Pract. Geol., p. 36, 1865. 

 — — Id. Mem. Geol. Survey, vol. iii, p. 267, 1866. 



Spec. Char. Shell small, semicircular, widest at the hinge-line, with small semi- 



