EXPLANATION OF THE PLATES. 
421 ' 
Explanation of the Plates. 
Plate XIII. 
Fio. 1. Acrothyra signata mut. prima n. mut. 2^ x 2\ x 1|- m. Mag. 
— a Ventral valve; — b Mould of interior of same; 
— c Ventral from the side; — d Another ventral with low 
umbo ; — e Dorsal valve ; — f Mould of the interior ; — g 
Dorsal from the side. From Coldbrook Group at Dugald 
Brook, Escasonie, N. S. See p. 382. 
Fig. 2. Acrothyra signata n. sp. 3x2x1 mm. Mag. ; — a Ventral 
valve; — b Mould of the interior; — c Ventral valve from 
the side ; — d Dorsal valve ; — e Mould of interior of same. 
From Assise E.16 (Lower Etoheminian), Dugald Brook, 
Escasonie. See p. 381. 
Fig. 3. A. signata mut. sera, n. mut., 2|^ x 2| x IJ. Mag. Lo • — 
Ventral valve ; — b Mould of interior of same; — c Ven- 
tral from the side ; — d Dorsal valve ; — e Mould of in- 
terior ; — -f Dorsal from the side. From Assise E. Ic 
(Lower Etchemin.) at Dugald Brook, Escasonie, N. S. 
See p. 383. 
Fig. 4. A. signata, mut. orta, n. mut., 2 x 1| x 1 mm. Mag. ; — a 
Ventral valve, mould of interior showing visceral callus ; 
— b Another narrower, showing traces of extension of 
the callus ; — c Ventral from the side ; — d Dorsal valve ; 
— e Mould of interior of the dorsal ; — / Dorsal from the 
side. From Assise E.2c (Lower Etchemin.) at Dugald 
Brook, Escasonie, N. S. See p. 385. 
Plate XIV. 
Fig. 1. Acrothyra signata mut. tarda, n. mut., 2^ x 3 x 1| mm. Mag. 
S” ; — a, Ventral valve from above ; — b Mould of interior 
of a ventral ; — c Same seen from behind ; — d Ventral 
valve from the side. From Assise E.lc? (Lower Etchemin.) ' 
at Dugald Brook, Escasonie, X. S. See p. 384. 
