ORDOVICIAN AND SILURIAN BRACHIOPODA OF THE GIRVAN DISTRICT. 933 



Horizon. — Mullock Hill Group. 



Locality. — Mulloch Hill. 



Remarks. — The transverse shape of this shell and long hinge-line and the surface 

 ornamentation distinguish it from the typical Strickl. lens. The transverse variety of 

 the latter, above described, from Woodland Point and Newlands, has not the coarse 

 concentric ridges nor the radial undulations. Pentamerus microcamerus, M'Coy, # 

 is closely similar in shape. 



Genus Pentamerus, Sowerby. 

 Pentamerus oblongus, Sowerby. 

 1839. Pentamerus oblongus, Sowerby, in Murchison's Silurian System, p. 641, pi. xix, fig. 10. 

 1866. Pentamerus oblongus, Sowerby, Davidson, Mon. Brit. Foss. Brack., vol. iii, pt. vii, p. 151, 



pi. xviii, figs. 1-12; pi. xix, figs. 1, 2. 

 1883. Pentamerus oblongus, Davidson, op. cit., vol. v, Silur. Suppl., pp. 161, 225. 



Typical examples of this well-known species occur, at Cuddystone Glen, Pen- 

 whapple Glen, and Penkill, and attain a length of 50-60 mm. I have not seen any 

 specimens from the Middle Llandovery of Newlands, as stated by Davidson. 

 Horizons. — (l) Penkill Group ; (2) Camregan Group. 



Localities. — (l) Penkill, Pen whapple Glen ; (2) Bargany Pond Burn, Cuddystone 

 Glen. 



Subgenus barrandella, Hall and Clarke. 

 Pentamerus {Barrandella) undatus (Sowerby). 

 1839. Atrypa undata, Sowerby, in Murchison's Silurian System, p. 637, pi. xxi, fig. 2. 

 1866. Pentamerus undatus (Sowerby), Davidson, Mon. Brit. Foss. Brack., vol. iii, pt. vii, p. 155, pi. xix, 



figs. 4-9. 

 1883. Pentamerus undatus, Davidson (pars), op. cit., vol. v, Silur. Suppl., p. 162, pi. ix, figs. 10-15, 19, 20 

 (nou figs. 16-18). 



A considerable number of specimens of a large subglobose transverse smooth 

 pentameroid, having the sinus on the pedicle-valve and the fold on the brachial valve, 

 occur in the beds at Woodland Point and Newlands, and are certainly referable to 

 Sowerby's Pentamerus undatus,^ sens, str., for they possess all the typical internal 

 and external features. Some of the specimens measure as much as 40 mm. in width. 

 The large swollen incurved beak of the pedicle-valve rising high above that of the 

 other valve and with a concave false area below it crossed by an open triangular 

 delthyrium are characters which serve to distinguish it from the transverse variety of 

 Strickl. lens, which occurs associated on the same horizon ; but crushed and imperfect 

 specimens, especially of brachial valves, are difficult to separate. Davidson figured 

 several examples of Pent, undatus from Woodland Point, but unfortunately included 

 some specimens (figs. 16-18) of Triplecia woodlandensis under this name (see p. 910). 



Horizons.— (\) Sa'ugh Hill Group ; (2) Mulloch Hill Group. 



Localities. — (l) Woodland Point, Newlands; (2) Mulloch Hill. 



* M'Cot, Ann. Mag. Nat. Hist., ser. 2, vol. viii, 1851, p. 290. 

 t Davidson, op. cit., vol. iii, p. 155, pi. xix, figs. 4-9. 



