BRITISH SILURIAN BRACHIOPODA. 159 



•var. rhomUctty M'Coy, Lept. tenuicinta^ Strophomena (jrandis, Sf. arenacea {?), St. 

 expansa, St. corrugatella, Orthis protensa, 0. calligramma, 0. biforata, 0. crispa, 

 0. elegantula^ and 0. testudinaria, forms that characterise the Caradoc. They occur in 

 the shape of casts in a course conglomerate with quartz pebbles. I found none of those 

 Llandovery and Wenlock forms such as Spirif. plicafella, Pentamerus ohlongus, Meristella 

 {?) angustifrons, Atrypa marginalis, OrtJiis Boukhardi, or Stroph. pecten, quoted in the 

 Explanation of Sheet 15, above noticed. Besides Dunterleugh Burn and Black Burn, 

 Wanlock Water, Dumfriesshire, the Leadhills species have been collected at Glentrip 

 Burn, Wallace's Cast, and Snar Water, in Lanarkshire. The specimens from all these 

 localities have been kindly forwarded to me for examination by order of the Director- 

 Oeneral of the Geological Survey of Great Britain. 



50. Rhynchonella Callawayiana, Dav. Sil. Sup., PI. X, figs. 18, 18 a, b, c. 



Shell small, elongated oval, much longer than wide ; dorsal valve evenly convex to 

 about half its length, fold biplicated, lateral slopes of fold large, one or two rudimentary, 

 rounded ribs on the lateral portions of the valve near the margin ; ventral valve 

 convex, sinus wide and shallow, with a short single mesial rib ; beak small, incurved. 

 Length 4, breadth 3, depth 3 lines. 



Obs. — Of this well-marked species one specimen only was procured by Dr. C. Calla- 

 way from the Wenlock Limestone at Walsall ; and it is with much pleasure I name it after 

 its discoverer. It differs by its shape from all the other British Silurian Bhynchonellce 

 hitherto discovered. 



51. Rhynchonella Portlockiana, Bav. Sil. Mon., PI. XXIV, figs. 23 — 25 ; Sil. 



Sup., PI. X, figs. 12, 13, 14. 



Since publishing the description of this species at p. 189 of my 'Silurian Mono- 

 graph,' Mrs. R. Gray has found several specimens of the shell in the Upper Llandeilo at 

 Balcletchie, Girvan, Ayrshire. These specimens agree in shape with those from the 

 Caradoc of the Chair of Kildare in Ireland. 



22 



