(1) 



(2) 



(3) 



24 



15 



25 mm. 



35 



22 



32 mm. 



ORDOVICIAN AND SILURIAN BRACHIOPODA OF THE GIRVAN DISTRICT. 911 



Surface of shell smooth, except for a few widely spaced fine concentric growth- 

 ridges near margins. 

 Dimensions. — 



Length 

 Width 



Horizon. — Saugh Hill Group. 



Locality. — Woodland Point. 



Remarks. — The affinities of this shell are with T. wenlockiensis, Davidson,* and 

 T. insularis, Eichw.,t but it differs from the former by the better defined fold on 

 the brachial valve, and from the latter by the sharp edges to the sinus on the pedicle- 

 valve. It bears a closer resemblance in these respects to the Clinton species 

 T. Ortoni, Hall,{ but is more transverse and less quadrate. Davidson's figure § of a 

 Llandovery shell referred to T. insularis from Minsterley bears more resemblance to 

 our Girvan species, and it seems indistinguishable from the Kashmir shell referred to 

 T. insularis by the author. || It is difficult to understand how Davidson confused 

 some of the better specimens belonging to this new species with the true Penta- 

 ■met'us undatus (Sowerby), which also occurs at Woodland Point associated with it, 

 though crushed and fragmentary shells are not easily distinguished. 



Genus Mimulus, Barrande. 



Mimulus ? incertus (Davidson). 



(Plate XX, figs. 17-23.) 



1870. Atrypa incerta, Davidson, Mon. Brit. Foss. Brach., vol. iii, pt. vii, p. 203, pi. xxiv, fig. 30 ; 



pi. xxv, figs. 7, 8. 

 1883. Triplesia incerta, Davidson, ibid., vol. v, Silur. Suppl., p. 145, pi. viii, figs. 24-28, 1 29. 



In this species the convexity and fold belong to the pedicle (ventral) valve, and 



the interior of this valve was figured by Davidson (op. cit., pi. viii, fig. 28) and 



correctly described as such in the text, but referred to as a "dorsal" valve in the 



explanation of the plate. The fold is often undifferentiated from the general swollen 



subcarinate rounded surface or is only developed near the front margin ; the beak is 



very high, acutely pointed, and more or less incurved, with the apex perforated by a 



small foramen ; the hinge-area is triangular and very high, and the wide flattened 



deltidium seems to have a narrow median slit or impressed line, if Davidson rightly 



interprets the markings on the hinge-area. Internally there seem to be small teeth 



in the pedicle-valve, but the interior of the beak is apparently filled up by a pair of 



thick plates completely fused together except in front, where they form thick short 



* Davidson, op. cit., vol. v, Silur. Suppl, p. 144, pi. viii, fig. 23; Hall and Clarke, Pal. N.Y., Brach., i, 

 pi. xic, fig. 22. 



t Davidson, op. cit., vol. iii, p. 273, pi. xxxvii, figs. 8-15. J Hall and Clarke, op. cit., pi. xic, figs. 12-20. 



8 Davidson, op. cit., vol. v, Silur. Suppl, p. 134, pi. viii, fig. 18. 



|| Reed, Mee. Geol. Surv. India, vol. xlii, pt. i, 1912, p. 27, pi. ix, fig. 14. 



