SOLENOMYA PRIMJSVA. 439 



Js'on SoLENiMTA ? PuiMABA, Youny and Armstrong, 1S71. Trans. Geo). Soe. Grlasg., 



vol. iii, SuppL, p. 54. 

 SoLENOMTA pbiMjIIVA, Arvistrong, Young, and Rolertson, 1876. Cat. West. 



Scottish Foss., p. 55. 

 SoLEMYA PEiM^TA (?), Bigsbij, 1878. Thesaurus Devouico-Carbonilerus, p. 313. 



— PuzosiANA, 5((/s6y, 1878. Ibid., p. 313. 



— — de Konincli, 1885. Anu. Mus. Eoy. Hist. Nat. Beige, vol. xi, 



p. 120, pi. xxiii, figs. 29, 33, 34, 

 and 41. 



— pbiMjEVA, Etheridge, 1888. Brit. Foss., pt. 1, Palseozoic, p. 291. 



— — var. /3 puzosiANA, Etheridge, 1888. Ibid., p. 291. 

 Sanguikolites eadiatus, Etheridge, 1888. Ibid., p. 289. 



Specific Characters. — Shell of medium size, transversely elliptical, very inequi- 

 lateral, slightly convex. The anterior end is by far the longer, gently conxex, its 

 margin bluntly rounded, ? gaping, broader from above downwards than the 

 posterior end. The inferior border is transverse and very slightly convex, almost 

 parallel with the superior margin. The posterior border is narrowed from above 

 downwards, and is elliptical. The superior margin is nearly as long as the shell, 

 straight in front and somewhat raised, depressed posteriorly. The umbones are 

 small, elongate, and compressed ; not elevated, excavated posteriorly, and placed 

 in the posterior third of the valve. The valves are much more convex from 

 above downwards than from before backwards, and there is an obscure 

 oblique compression, sometimes almost obsolete, about the centre of the valve. 

 The upper margin of the valve is expanded from side to side, and flattened from 

 above downwards. Behind the umbones there is a broad and short escutcheon. 



Interior. — The anterior adductor muscle-scar is large, pear-shaped, shallow, 

 placed some short distance from the margin and just below the hinge-line. The 

 posterior adductor scar is smaller, deeper, more circular, bounded in front by a 

 shallow ridge, and situated just beneath the upper margin, but slightly remote from 

 the posterior edge. Pallial line faint, but entire. The inner surface is smooth in 

 the umbonal region, but is crossed by radiating, flattened ribs. These are not 

 prominent, close together towards the anterior and posterior ends, but more 

 widely separated over the centre of the valve, where thej are often bifurcate. 

 The ribs are chiefly directed downwards and forwards from the umbo, being 

 obsolete at the posterior end. 



Exterior. — Very rarely seen, but fragments show the same kind of ornamenta- 

 tion as that impressed on casts of the interior, but stronger, and there are also 

 present almost obsolete concentric lines or folds. Periostracum wrinkled. Shell 

 very thin. 



Dimensions. — PI. L, fig. 2, the type (unfigured) from which Portlock described 

 the species, measures — 



