208 BRITISH CARBONIFEROUS BRACHIOPODA. 



Spec. Char. Shell very variable in shape, but usually more or less regularly elliptical 

 or ovate, with its greatest width either towards the posterior or anterior extremity. Its 

 sides are also sometimes nearly parallel and rounded in front, but both front and beaks 

 are in some examples about equally and regularly elliptically attenuated. The valves are 

 generally gently convex, and most elevated along the middle, where there exists likewise a 

 flatness, which becomes gradually wider as it extends from the apex of the beak to the 

 front, the lateral portions of the valves sloping rather abruptly on either side, while the 

 surface is marked at intervals by a greater or smaller number of concentric ridges or lines 

 of growth. Interior unknown. Dimensions variable ; three British examples have 

 measured — 



Length 10, breadth 5^ lines. 

 7 'li 



)) " >} *■ 2 >J 



Obs. After the examination of a considerable number of specimens, it has appeared 

 to me that L. parallela and L. elliptica are only slight variations in shape of Sowerby's 

 L. mytiloides ? Some palaeontologists will, however, probably differ with me in this con- 

 clusion, and may prefer retaining L. mytiloides and L. parallela as separate species, and I 

 should be glad to adopt their views if they can point out the characters by which the two 

 can be distinguished. It will, perhaps, be as well, therefore, to reproduce the original 

 description and figures. Sowcrby describes L. mytiloides as follows : 



" Ovate, anterior end slightly truncated ; beak indistinct. Nearly an inch long, and 

 three fifths wide ; the older shells are flattened towards the front, with rather a straightish 

 edge. Shining, and of a grayish-blue colour. 



" These arc mostly found in pairs at Wolsingham, in the county of Durham, in a dark- 

 coloured limestone. I am told they are sometimes larger than the figure. They are pre- 

 served so well that they have the appearance of a recent mussel." 



Phillips describes his species as follows : 



" L. elliptica. — Long, elliptical, acuminated retrally, surface with delicate, radiating, 

 and concentric lines. Ashford, in Derbyshire. 



" L. maryinata. — Very oblong, with parallel sides, truncate in front, rounded retrally ; 

 edges of the valves turned up; slight mesial ridge on a flat space; small, oval hollow, fine 

 radiating and concentric lines. Bowes. 



" L. parallela. — Magnified views of a species which seems different from the last by its 

 rounded front and equally convex surface. Northumberland." 



Besides the English localities above given I have seen specimens from the Carboniferous 

 shales of Brakewell and Ashford, in Derbyshire ; Denwich, Northumberland. In Scotland 

 it occurs abundantly in slaty ironstone in the parish of Carluke, in Lanarkshire, at 160 

 fathoms below the " Ell Coal," 239 at Gare, 300 at Mashock Burn, 237 at Raes Gill, 

 Braid wood, and Langshaw Burn, 371 at Kilcadzow. It occurs likewise at Hall Hill, near 

 Lesmahago, Capelrig, East Kilbride ; Calderside and Auchentibber, High Blantyre ; 



