ORDOVICIAN AND SILURIAN BRACHIOPODA OF THE GIRVAN DISTRICT. 811 



Lingulasma ? tenax, sp. nov. 

 (Plate III, figs. 5, 6.) 



Shell broadly oval ; sides gently arched outwards ; anterior end rounded, not 

 truncate. Pedicle-valve acuminate, with short pointed beak ; shoulders meeting at 

 right angles or less and extending less than one-third the length of shell. Brachial 

 valve with more obtuse beak. Surface of valves ornamented with very fine closely 

 placed minutely undulated concentric lines bearing numerous regular equidistant 

 minute granules of equal size, obscurely and rather irregularly arranged in radiating 

 lines. Inner layer of shell with fine radiating striae. 



Dimensions. — Length, 18 "5 mm ; width, 14'0 mm. 



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



Localities. — (l) Woodland Point ; (2) Penkill. 



Remarks. — As the interior is unknown the reference to Lingulasma is doubtful ; 

 but the ornamentation is of the same type as that described in L. pulcherrimum. 

 The granules are not so large nor so close nor so numerous as in that species, and 

 the shell is much broader and shorter. The concentric lineation is more conspicuous 

 than the radial arrangement of the granules. L. scobina, Williams,* from the 

 Silurian of Maine, appears to have a somewhat similar ornamentation. 



Genus Siphonotreta, De Verneuil. 



Siphonotreta micula, M'Coy. 



1851. Siphonotreta micula, M'Coy, Ann. Mag. Nat. Hist., ser. 2, vol. viii, p. 389. 



1852. Siphonotreta micula, M'Coy, Synopsis Brit. Pal. Foss. Woodw. Mus., p. 188, pi. iH, fig. 3. 

 1866. Siphonotreta micula, M'Coy, Davidson, Mon. Brit. Foss. Brach., vol. iii, p. 76, pi. viii, figs. 2-6. 

 1883. Siphonotreta micula, M'Coy, Davidson (pars), op. cit., vol. v, Silur. Suppl., p. 224. 



Some small shells from Ardmillan, Dow Hill, and Balclatchie appear to be refer- 

 able to this species, the exterior of one specimen showing the numerous delicate 

 short spines on the edges of the concentric laminae and the others the bases of 

 similar spines. The terminal foramen on the short beak of the pedicle-valve can also 

 be detected. 



Dimension. — Length, 2'5-3"0 mm. 



Horizon.— Balclatchie Group. 



Localities. — Ardmillan, Dow Hill, Balclatchie. 



Siphonotreta ? thraivensis, sp. nov. 



(Plate III, figs. 7, 8.) 



Shell broadly ovate, nearly as wide as long. Pedicle-valve with short acuminate 



perforated beak, shoulders meeting at about 90° ; sides of valves gently arched, 



* Williams, Proc. U.S. Nat. Mus., vol. xlv, 1913, p. 339, pi. xxx, fig. 18. 

 TRANS. ROY. SOC. EDIN., VOL. LI, PART IV (NO. 26). 118 



