MONTAGUL’S BRITISH SHELLS. 
Under the genus donax, the additions 
are the complanata and the plebeia, 
noticed before only by Lister; and the 
castanea, a nondescript. ‘Vhe error of 
Pennant in calling the donax irus of Lin- 
nzus, tellina cornubiensis is also recti- 
fied. This species perforates the hardest 
lime stone. Its animal inhabitant is an 
ascidia, and nota tethys; which is pro- 
buably the case with most which perforate 
other bodies. 
The additions‘to the genus Venus are 
the paphia, pectunculus fasciatus of Da 
Costa; the tigrina of Linnezus: the 
ranulata of Gmelin: the pullastra of 
r. Wood: the minima, the subcordata, 
the triangularis, the spinifera, and the 
perforans, nondescripts. Penmant’s ery- 
cina is determined to be the verru- 
cosa of Linnzus ; his rugosa, the gal- 
lina of Gmelin and our author’s stria- 
tula ; his mercenaria the islandica, and 
not the mercenaria of Linneus, which 
is the wampum of the American Indians, 
and has not been found on our coasts ; 
and his litterata, the decussata. 
The chama is rendered a British ge- 
nus, for the first time, by the insertion 
of the chama cor, found about the He- 
brides. 
Under the genus Arca, the glycimeri$ 
of Pennant is referred to tlfe pilosa of 
Linnezus on the authority of Pulteney ; 
the barbata to. the lactea, in opposition 
to Pulteney ; and the tortuosa to the 
noz. The minuta of Gmelin is the only 
addition. 
The genus ostrea is divided into two, 
after Pennant and others; those which 
are aurited being separated from the 
rest under the generic denomination of 
pecten. A difference also is poimted 
out in the hinge, that of the pectem 
having a small sub triangular, that of the 
Ostrea, a transverse, striated cavity. 
The lineatus, first noticed by Dr. 
Pulteney, and sent by him to. Da Costa, 
is the only addition to Pennant’s species 
of pecten. His subrufus is referred to 
the opercularis of Linneus. \ 
The ostrea striata of Donovan, first 
noticed by Lister, is in the body of the 
work, added to the edulis, the only spe- 
cies in Pennant, but in the appendix is re- 
moved to the genus anomia. Mr. Mon- 
‘tague has recently taken alive a few large 
and: strong specimens, adhering to 0 
bivalves. 
The aculeata and undulata of Gmelin 
‘are the only 4 lditions to the genus ano- - 
mia. The squamula is supposed to be 
857 
the young of the ephippium, and the 
cepa not to be distinct from it. 
Tothe mytili of Pennant are added 
the crista galli and discors of Linneus 3 
the avonensis, which seems to have been 
described by Lister; the striatus from 
Walker; the ungulinus of Donovan; 
and the przcisus, resembling the solen 
minutus, and the discrepans, nonde- 
scripts. 
The following original observations 
annexed to this genus will give pleasure 
to our readers. 
<< We shall here take the liberty of remark- 
ing, that very great attention is requisite to 
disctiminate some of the minute bivalve 
shells, and separate them from the bivalve mo- 
noculi. 
‘<The great affinity that the coverings, or 
shells, of some of this class of insects, bear to 
the testacea tribe, has in all probability caused 
many to have been considered as small spe- 
cies of mytilus, or the fry of larger ; for man 
such monoculi are capable of shutting their 
valves intirely, and iodloang every part of the 
animal : in which state they always are when 
dead, so that it is mo easy matter to discrimi- 
nate. 
«< Mr. Walker is not the only one who has 
fallen into this error, in his figures 76, 77, 
and 78, all of which we have received from 
Sandwich, and have found them in other 
parts. ‘4 
«© The first is found in fresh-water, and is 
not much unlike monoculus conchaceus, 
Gmnelin Syst. p. 3003, but is longer, in pro- 
portion to its breadth, than the figure given 
of that insect by Donovan, British Insects, 
1. tad. 
“« The other two, given by Mr. Walker, 
are marine monoculi; both found on oysters, 
and other rugged shells: and is not uncom- 
mon on the coast of Devon: especially No. 
77, about the byssus of the pinna ingens : 
both these appear to differ only in shape, 
and do not seem to have obtained a place 
amongst the apterpus insects. When ex- 
amined under a microscope, the shells are 
punctured all over. ; 
-*© To these supposed mytili of Mr. Walker, 
we may add the monoculus conchaceus, 
which has been sent to us for such ; and we 
could enumerate many others, which inhabit 
both salt and fresh-water, that might readily 
be mistaken for minute shells : one of which 
is figured in Tab. 14 No. 8. of this work by 
mistake, not having an opportunity of ex~ 
amining the aniimal till after the plate was en- 
graved. * 
«This and another species of monoculus 
in every respect like it, but of a longer and 
more cylindric shape, is found on oysters on 
the south coast oF Devonshire; and on the 
byssus of the pinna ingens}; a general repos 
sitory for monoculi and very minute shells, 
especially nautili and vermiculi. 
«These two species of monoculus are ex- 
tremely smovth and glossy, of a blush-cos 
