514 DR WHEELTON HIND ON 



Locality. — Upper Bala, Star-fish bed. 



Observations. — Two specimens, a right and a left valve, are in the Gray Collection. 

 The latter shows the hinge plate, and both are casts of the interior, but show indications 

 of the surface ornament. Salter's C quadrata, sp., has something of the appearance of 

 C transversa, but the latter has an expanded posterior end, and the upper and lower 

 margins are not so nearly parallel. 



Genus Vanuxemia, Billings, 1858. 



Vanuxemia, Billings, 1858, Rep. Prog. Geol. Surv. Canada, p. 186. 

 „ Miller, 1889, North Amer. Geol. and Pal., p. 515. 



,, Ulrich, 1897, Geol. Minnesota, Final Rep., vol. iii., pt. ii., p. 549. 



Generic Characters. — Shell ventricose, oblique, very inequilateral. Umbones an- 

 terior, raised, incurved, distant, a well-marked ligamental area. 



Interior. — Hinge plate massive, with two to four oblique cardinal and lateral teeth. 

 Anterior adductor muscle scar deep, and placed apparently in a hollow of the anterior 

 end of the thickened hinge plate. Pallial line entire. 



Exterior. — The surface is marked by fine lines of growth. 



Observations. — The umbones of Vanuxemia are more terminal than those of 

 Cyrtodonta, to which it has a close affinity, as demonstrated by the structure of the 

 hinge plate. Ulrich (op. supra cit.) points out the important difference in the position 

 of the anterior adductor muscle scar " being excavated out of the hinge plate instead of 

 being placed on the floor of the valve." He says he knows twenty to twenty-five valid 

 species, all of Lower Silurian age. 



Vanuxemia distans, sp. nov. (PI. V., figs. 31-33.) 



Specific Characters. — Shell small, obliquely gibbose, subquadrate. The anterior end 

 is compressed and thin, subalate ; its margin descends and curves backwards, the inferior 

 border is narrowed and rounded, the posterior margin almost straight, oblique, the 

 hinge line straight. The umbones are large and pointed and incurved, and twisted 

 slightly forwards, widely separated and elevated, subcentral. The valve is obliquely 

 swollen, the dorsal slope subalate. 



Interior. — The posterior hinge teeth are normal. Unfortunately, no more details are 

 exposed. 



Exterior. — Ornamented with fine concentric lines of growth. 



Dimensions.- -Fig. 33, PI. V., a right valve, measures: an tero- posteriorly. 19 mm. ; 

 dorso-ventrally, 12 mm. ; gibbosity of valve, 7 mm. 



Locality. — Scotland : Llandeilo beds, Balclatchie, Dowhill, Craighead. 



Observations. — This peculiarly shaped shell resembles the gasteropod Capulus in 

 shape, but, as I find both right and left valves, there is no doubt that it is a Pelecypocl. 

 There are several specimens in the Gray Collection from the above localities. Several 



