ORDOVICIAN AND SILURIAN BKACHIOPODA OF THE GIRVAN DISTRICT. 807 



Lingula quadrgtta, Eichwald. 



1829. Lingula quadrata, Eichwald, Zool. Special., vol. 1, p. 273, pi. iv, fig. 2. 



1883. Lingula quadrata, Eichwald, Davidson, Man. Brit. Foss. Brack., vol. v, Silur. Suppl., p. 203, 

 pi. xvii, figs, 2, 3. 



This species is fairly common in an imperfect condition at Craighead, and 

 Davidson's identification appears to be correct. Gagel* describes it from the 

 Ordovician pebbles of Prussia. It grows to a large size, one of Davidson's figured 

 specimens measuring about 35 mm. in length. The closely allied or identical species 

 from the Trenton and Lorraine Formations is known as L. rectilateralis, Emmons, t 



Horizon. — Stinchar Limestone Group. 



Locality. — Craighead. 



Lingula solvens, sp. no v. 

 (Plate II, fig. 19.) 



Shell almost subquadrate ; sides slightly arched outwards, subparallel ; anterior 

 end bluntly rounded ; beak obtuse ; shoulders short, meeting at about 120°-130°. 

 Surface of shell ornamented with very regular equal and equidistant concentric 

 lines ; interior marginally marked with irregular vascular branches. 



Dimensions. — Length, 34 mm. ; width, 24 mm. 



Horizon. — Drummuck Group (Starfish Bed). 



Locality. — Thraive Glen. 



Remarks. — In shape this shell is much like the specimen referred to L. ovata, 

 M'Coy, from the Chair of Kildare, which was figured by Davidson,! but the latter 

 seems distinct from M'Coy's type of L. ovata from Ballygarvan, Wexford. There is 

 only the one good specimen here measured which I have seen of this species from 

 Girvan, and it is in Mrs Gray's collection. L. ioivaensis, Owen,§ of the American 

 Ordovician appears to resemble it in shape. The interior of our species is unknown. 



Lingula Symondsi, Salter. 



1866. Lingula Symondsi, Salter MS., Davidson, Mon. Brit. Foss. Brack., vol. iii, pt. vii, p. 45, pi. iii, 



figs. 7-17 (? all). 

 1883. Lingula Sysmondi [sic], Davidson, op. cit., vol. v, Silur. Suppl., p. 224, pi. xvii, figs. 23, 24. 



The occurrence of this species in the Girvan district seems tolerably certain, but 

 none of the specimens which I have seen, including those which Davidson identified, 

 are quite satisfactorily preserved. 



Horizons. — (l) Saugh Hill Group ; (2) Camregan Group ; (3) Penkill Group. 



Localities. — (l) Woodland Point ; (2) Bargany Pond Burn ; (3) Penkill. 



* Gagel, " Brach. camb. silur. Gesch. Ost- u. Westpreussen," Beitr. natur/c. Preussens, vi, 1890, p. 19, t. i, fig. 9. 

 t Ruedemann, Bull. 162, New York State Mus., 1912, p. 91, pi. iv, fig. 1. 



* Davidson, Mon. Brit. Foss. Brack., vol. iii, pt. vii, pi. ii. fig. 20 (non cet.). 



§ Winchell and Schuchert, Falseont. Minnesota, iii, p. 349, pi. xxix, figs. 19-22. 



