[MATTHEW] CAMBRIAN FAUNAS 211 
ACROTRETA Of BAILEYI.! 
A thin-shelled form which has suffered much from compression, 
is not rare in the Mt. Stephen shale. As in A. Baileyi the area of 
the ventral valve is quite short, and the median ridge of the interior 
of the dorsal has the broad lance-formed end of that of Linnarssonia. 
Sculpture. This consists of very fine concentric striæ, somewhat 
obscured by a minute granulation. 
Size. Length, 34 mm.; width, 4 mm.; height (as compressed in 
the shale) less than 1 mm. 
This species is very Linnarssonia-like but the beak is too sharp 
and too much elevated for that genus; also the smooth shining shell 
of Linnarssonia is wanting. 
LEPTOBOLUS cf. GRANDIS.” 
A number of examples of a small brachiopod were found, which 
by its size and form comes near the above species.! It is a thinner 
and flatter shell but the difference may be due to the occurrence in 
shale in place of sandstone. There is less difference in the compara- 
tive length of the two valves than in L. grandis, and the sculpture 
also is different. Sculpture consists of faintly marked fine, concentric 
striæ, with more distinct undulations cf growth, the whole obscured | 
by a minute granulation. 
It is distinct from Halls species of the Utica slate in the absence 
of minute concentric striæ, distinct, close and regular, also in its 
larger size. 
Merorroma AMI, n. sp. (Plate 1, fig. 12). 
Examples of this shell are usually much flattened and the natural 
form obscured. The apex was usually somewhat excentric and was 
acuminate. Outside of the acuminate apex the slopes of the shell 
were convex, and so continued to the margin. 
Sculpture. Only very faintly marked radiating striæ are visible 
and a few concentric undulations of growth. 
Size. Length of orifice 10 mm.; width, 84 mm.; height (as com- 
pressed in the shale), 2 mm. 
This species was not quite so large as Metoptoma Barrandei, 
Linrs., and differed in its smooth surface. It was much flatter and 
was smaller than the Metoptome of the Potsdam sandstone of Wis- 
consin. 

* Trans. Roy. Soc. Can., Vol. IIL, p. 36, pl. v., figs. 13, 13 @ b c. 
? Trans. Roy. Soc. Can., Vol. XI., p. 91, pl. 16, figs. 7a to c. 
