BULLETIN OF THE NATURAL HISTORY SOCIETY. 
vening ridges narrowed ; this layer has a shining surface. Beneath 
this is a third layer on which the stria? run in an opposite direction 
from those of the one above, the sculpturing, especially along the 
central part of the valve, consisting of stria? radiating from the um- 
bonal region to the front margin ; these are crossed at intervals by 
undulations of growth concentric to the umbo ; on the inside of this 
layer are impressed the surface markings of the interior of the valves. 
Size.- — Length, 5 to 5J mm. ; breadth, 4 to 5 mm. ; depth of 
each valve, about 1 mm. The ventral is about \ mm. longer than the 
dorsal. One dorsal has a length of 6 mm. 
Horizon and locality . — In calcareous sandy layers with the Peltura 
fauna at McAdarn shore, Escasonie, Cape Breton. This species was 
not found in situ, but in loose pieces of thin flag in the shingle of the 
shore where the trilobites occur ; these pieces were very little worn, 
and therefore near or at the parent ledge. This species may be re- 
ferred to the Peltura zone (36). 
This species is referred doubtfully to Lingulella as it has some 
characters of other genera. The weak cardinal development is like 
Leptobolus ; as is the long lateral ridges and advanced (“ j ”) laterals 
of dorsal valve. The spreading vascular trunks of the ventral valve 
are like Leptobolus and Obolus, as also the advanced “ j ” lateral. On 
the other hand the thick shell is quite unlike Leptobolus, but common 
in Obolus and Lingulella. 
This pretty little species is easily recognized by its peculiar trans- 
verse sculpture. Lingula teneola, Hall, has a similar transverse orna- 
mentation, but it is much larger, and flourished at a later period 
(Clinton group).! 
Lingulella Ella, H. and W., has a somewhat similar sculpture, 
but is distinguished by its greater size, and the closer approximation 
of the vascular trunks of the ventral valve. 
It is only in a few valves out of many that we find distinct muscle 
scars, enabling us to compare the species with others. Michwitz has 
determined that the exterior half of the great central muscle in the 
ventral valve of Obolus represents the “ 1 ” lateral of Lingula.* In 
this relation it is interesting to observe that the great muscle in 
L. (?) Escasoni also has a septum partly dividing it; but there is a 
separate scar, a small triangular one, at the anterior outer angle of 
* Mem. Acad. Imp. des Sci. St. Petersbourg. Series VIII. Tom, IV., No. 2, p. 79. 
t N. York State Geologists’ Report. Hall & Clarke, 1 891, pi. i, fig. 8. 
