DOWLING. 
SILUIHAN FOS.SILS 
45 F 
though the umbo and l)eak of the latter are broken off. Both are 
transversely subedliptical in outline and wider than long, and both 
have a rather shallow inai’ginal sinus in the ventral valve. They arc 
entirely ribless, but the better jtreserved one of the two i.s (inely and 
nodo.sely cancellated by numerou.s, clo.se-set, minute concentric ridges, 
that are crossed by .similar radiating ones. 
At the portage road at the falls a specimen, with the same general 
.shape and with a -similar sinus in the ventral valve, was collected, but 
it is so much worn that its surface markiim's are tjuite oliliterated, and 
the beak of the ventral is so imperfect that it is impo.s.sible to tell 
whether it was oiiginally perforate or not. Tliis .•'pecinum .‘^eems to 
correspond fatr)y well with E. Billings’ figures of Atlnrrh Blanch a, 
from the Silurian rocks of iMaine, which Hall and Clarke refer to 
Merutinn, but whicli Schuchert says is a Meristella. 
Meristina (1) c.i'pant'a, sp. nov. 
Shell tumid, regularly and rather strongly hiconve.x, tr.insversely 
suhelliptical an<l always a little wider than long ; front margin of the 
valves not at all sinuated , surface entirely devoid of any kind of 
ribs. 
Ventral valve with a rather depres.sed though slightly prominent 
umbo, and an incurved l)eak. 
Dorsal valve with a much more depressed umbo and a smaller beak. 
Surface markings of the e.Kterior of the test unknown, those of its 
e.vfoliated inner layer consisting of mimer<^tu.s, close-set and very 
minute, concentric raised lines, as well a.s of a few rather distinct con- 
centric lines of growth ; .structure of the test fibrous. 
Characters of the interior of the valves unknown, though there i.s 
clearly a long mesial septum in the ventral valve, and apparently a 
similar one in the dorsal. 
Ekwan river t portage road at falls, one ^pecimcn : and foot of 
portage road, an unusually large but imperfect specimen. Attawa- 
piskat river, seventefTi to thirty miles below Rainy island, Dr. R. 
Roll, 1S8G ; eight .specimens. 
The.se specimens are mere ca->fs of the interior of the closed valve-s 
with small portinns of the inner layer of the test attached to some of 
them. It is by no means clear whether the beak of the ventral valve 
of any of them is perforate or not. They are provisionally and very 
doubtfully referred to Meristimi, on account of their general resem- 
b’ance in e.xternal form, to the European Af. tuinidn, but it may be 
