BRITISH SILURIAN BRACHIOPODA. 109 



68. Lept^na sericea, /S'oe^;. Dav., Sil. Mon., PL XLVIII, figs. 10—19; Sup., PI. 



XII, figs. 8—10. 



This abundant, long-lived, and widely-spread species has been fully described and 

 illustrated at p. 323 of my ' Silurian Monograph.' It takes the place of the Upper- 

 Silurian Lept. transversalis in the Lower-Silurian rocks. It is, however, sometimes 

 difficult to separate the two shells, although they differ internally, as well as by the very 

 slight general incurvature of the beak in the form under description. 



LepfcBna sericea occurs in the Lower-Llandovery, Caradoc, and Llandeilo formations. 

 In Scotland Mrs. R. Gray found it to abound in the Upper Caradoc at Thraive, in the 

 Middle Caradoc at Shallock Mill, in the Upper Llandeilo at Ardmillan Brae, Doularg, 

 Craighead, and Balcletchie. 



The Geological Survey of Scotland have collected specimens from the Caradoc at 

 Glencotho Quarry, near Broughton, at Kilbucho, near the church, one mile and a quarter 

 west of Culter, in Peebleshire, at Dunterleugh Burn, Wanlock Water, Leadhill District, 

 Dumfriesshire, and at Snar Water, near the Leadhills, in Lanarkshire, also at Gipsy Point, 

 in Kirkcudbrie-htshire. 



69. Lept^na sericea, var. rhombica, M'Coy. Dav., Sil. Mon., PI. XLVIII, figs. 



20—22 ; Sup., PI. XII, figs. 4—7. 



I have described this variety at p. 325 of my ' Silurian Monograph,' and I still feel 

 uncertain whether it should or not be considered specifically distinct from the much 

 smaller Lepiana sericea. Some specimens that have passed through my hands have 

 measured fully 1 inch in length by more than 1 inch 3 lines in breadth. Very large 

 and fine examples have been found by Mrs. R. Gray in the Upper Llandeilo at 

 Balcletchie in Ayrshire; and the Scottish Geological Survey has a very fine specimen, or 

 rather internal cast, obtained at Dunterleugh Burn, Wanlock Water, Leadhills, 

 Dumfriesshire. It occurs there in a conglomerate with quartz pebbles along with other 

 Caradoc species. 



70. Lept^na qtjinquecostata, 77/'Cbj/. Dav., Sil. Mon., PI. XLVIII, figs. 23—27; 



Sup., PI. XII, figs. 13, 13a, h. 



I have nothing to add to what I stated with respect to this species at p. 322 of my 

 ' Silurian Monograph,' further than that Mrs. R. Gray collected specimens of the shell 



