ORDOVICTAN AND SILURIAN BRACHIOPODA OF THE GIRVAN DISTRICT. 935 



with median group of 6-8 low rounded closely-placed longitudinal plications forming 

 broad weak flattened fold, arising at about half the length of the valve and most 

 developed close to anterior margin, scarcely elevated above smooth lateral portions ; 

 beak high, pointed, incurved, rising well above arched hinge-line, with a weak ridge 

 on each side curving off to define imperfectly a slightly depressed false area ; large 

 open triangular delthyrium below beak. Interior of valve with small spondylium and 

 very short median septum. Brachial valve with lower beak and slightly excavated 

 shoulders and weaker -flattened median fold composed of 5-7 longitudinal plications 

 like those on opposite valve ; lateral portions of valve smooth. Interior of valve 

 with pair of long parallel closely placed septa extending more than one-third length of 

 valve ; crura long, stout, recurved, diverging at about 60°, close to hinge-line ; posterior 

 adductors large, oval, lying against septa and extending to their extremities ; anterior 

 adductors small, deep, subtriangular, situated immediately in front of posterior pair 

 near middle line. Shell substance thick, fibrous, and externally punctate. 



Dimensions. — 



Brachial valve. Pedicle-valve. 



Length . . - . . 27 c. 35 mm. 



Width 25 c. 28 mm. 



Horizon. — Balclatchie Group (conglomerate). 



Locality. — Balclatchie. 



Remarks. — Davidson figured (op. cit., pi. ix, fig. 27) one pedicle-valve showing the 

 internal cast of the spondylium, but the rest of the specimen is not well preserved, 

 though the longitudinal plications are seen, so that his figure is a restoration. In 

 another figure (fig. 29) the beak and open delthyrium of the pedicle-valve are shown ; 

 but this specimen shows the median septum through the shell and a shallow groove 

 along the low median fold on the surface. The third figure (fig. 28) represents a 

 brachial valve, and shows the two median septa to some extent. But the best in- 

 terior of a brachial valve, mounted on the same tablet, was not figured by him, 

 and this cast shows the crura, septa, and muscle-scars (PI. XXIII, fig. 18). 



It does not seem possible to keep this pentameroid species in the genus Camarella, 

 which Hall and Clarke * suggested as its probable place, for the strong elongated 

 crura in the brachial valve are peculiar, and, moreover, in Camarella there is no 

 pair of median septa in the brachial valve. The muscle-scars of the brachial valve 

 are closely similar to those of Parastrophia.]' But the high beak of the pedicle- 

 valve and the open delthyrium, as* well as the spondylium in this valve, forbid us 

 placing it in the last-mentioned genus. The very thick fibrous and punctate shell is 

 another distinctive feature of our Balclatchie species, and on the whole it seems to 

 merit a new genus for its reception, and the name Metacamarella is proposed as 

 an indication of its affinities. 



* Hall and Clarke, Palxont. New York, vol. viii. Brach., ii, p. 221. 

 f Ibid., p. 387, pi. lxiii, fig. 21. 



