ORDOVICIAN AND SILURIAN BRACHIOPODA OF THE GIRVAN DISTRICT. 951 



Genus Spirifer, Sower by. 

 Spirifer plicatellus, var. radiata, Sowerby. 



1825. Delthyris lineatus (radiatus), Sowerby, Miner. Gonchol., vol. v, p. 493, figs. 1, 2. 

 1866. Spin/era plicatella, var. radiata (Sowerby), Davidson, Mon. Brit. Foss. Brack., vol. iii, pt. vii, 

 p. 87, pi. ix, figs. 1-6. 

 Spirifera plicatella, Davidson, op. cit., vol. v, Silur. Suppl., p. 137, pi. viii, figs. 2, 3. 



In these shells the lateral lobes are devoid of folds, as is the case in Sowerby's 

 original # type from the Wenlock Limestone. It appears to be rare in the Girvan area. 

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

 Localities. — (l) Penkill, Penwhapple Glen ; (2) Bargany Pond Burn. 



Genus Cyrtia, Dalman. 

 Cyrtia exporrecta (Wahlenberg). 



1821. Anomites exporrectus, Wahlenberg, Nov. Act. Reg. Soc. Scienf., vol. viii, p. 64, No. 3. 



1866. Cyrtia exporrecta (Wahlenberg), Davidson, Man. Brit. Foss. Brack., vol. iii, pt. vii, p. 99, pi. ix, 



figs. 13-24. 

 1883. Cyrtia exporrecta (Wahlenberg), Davidson, ibid., vol. v, Silur. Suppl., p. 137, pi. viii, fig. 4. 



This is a rare shell in the Girvan district, but the few specimens observed show 

 all the characteristic features, and the internal structure is seen in casts to agree with 

 typical examples of the species. 



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



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



Genus Rhynchospira, Hall. 



Subgenus homceospira, Hall and Clarke. 



Rhynchospira (Homoeospira) Bouchardi (Davidson), var. nov. mullochensis. 



(Plate XXIV, figs. 44-46.) 



Shell transversely oval to subtrigonal, biconvex. Pedicle- valve uniformly convex ; 

 beak acutely pointed, high, slightly incurved ; surface ornamented with 1 median 

 straight rib and 8-9 similar or rather smaller low rounded ribs on each side, closely 

 placed and curving slightly outwards. Brachial valve shorter than pedicle-valve, 

 with small low inconspicuous obtuse beak and shallow median sinus holding 1 fine 

 straight median rib (or none?), with 9-10 rather stronger ribs (similar to those on 

 other valve) closely placed and curving slightly outwards on the gently swollen lateral 

 lobes ; interior with median septum extending about half the length of the valve. 



Dimensions. — Length about 5 mm. 



Horizon. — Mulloch Hill Group. 



Localities. — Mulloch Hill, Craigens ? 



Remarks. — This small shell may be regarded as a variety of Rh. Bouchardi 

 (Dav.),| of the Wenlock Beds, but it differs in its more transverse shape, the presence 



* Davidson, op. cit., vol. iii, pi. ix, fig. 1. t Davidson, op. cit., vol. iii. pt. vii, p. 127, pi. xii, figB. 26-30. 



