16 
The specimen fig. 5. is from Ologhraii in the county 
of Dublin, and was given me by Mr. Joseph Hum- 
phreys. Fig. 6 is from Derbyshire, through the kind- 
ness of the late Mr. Salt; it is by no means an uncom- 
mon shell in the Mountain Limestone. I have quoted 
Martin’s figures with a doubt, because my specimens 
are not enough reticulated to agree with them, though 
they are probably only varieties of his seinireticulatus. 
PRODUCTUS concinnus. 
TAB. CCCXVI1I. — Fig. 1 . 
Spec. Char. Semicylindrical, convex above, 
with a concave front and narrow back, 
neatly striated and spinous ; lesser valve 
fiat, deeply inserted. 
A polished, thin, evenly made shell, much resem- 
bling P. Martini, but smaller and smoother. 
Found in very dark brown Limestone in Derbyshire 
and near Richmond in Yorkshire. The flat space 
around the edge of the lower valve occurs also in P. 
Martini, as Mr. Martin’s excellent figure shews, but it 
does not appear to be constant. 
PRODUCTUS lobatus. 
TAB. CCCXVII1. — Figs. 2 to 6. 
Spec. Char. Bilobed, very convex, furrowed, 
and spinous ; spines few. 
In general form much like P. Martini, but divided 
into two lobes by a deep cavity along the front ex- 
tending to the beak : the sulci or deep strise are few, 
and the hinge as long as the shell is wide, whicdi is 
seldom three-quarters of an inch. 
Fig. 2 exhibits two views of a specimen, in which 
the shell is almost rotten : it is from the same locality 
as the following. 
Figs. 3 and 4 are remarkably elongated : they are 
from a kind of Marie, probably decomposed Limestone, 
that occurs in Well Houses farm, belonging to the Rt. 
Hon. and Rev. Lord Charles Annesly, at his seat 
called Little Park Tower, in Northumberland, and are 
accompanied by P. Concinnus. 
Fig. 5 is in Limestone ; it was collected by Dr. 
W. E. Leach on the Island of Arran. 
Fig. 6 is from a cast in Sandstone, and shews the 
bases of four spines very regularly placed : it is from 
Cumberland. 
I have this species also from Derbyshire. 
