the Po, eom n E a 135 
e examined by me, there is not die slightest 
dissimilarity in the form of the ba ipi in 
either valve. 
In the following monograph of the Tracie so far as. 
known to me, I have endeavored to give the synonymy 
of each species, freed from the erroneous references of 
previous writers, before the confusion already existing 
should become inextricable. In prosecuting this at- 
tempt, every work referred to has been carefully ex- 
amined, with the exception of the Dorset Catalogue, and 
Donovan’s British Shells. Notwithstanding the pains 
which have been taken in comparing the observations 
of others and tracing each species to its original de- 
scriber, error may not have been entirely avoided on 
my own part. Still it is hoped that the present, if not 
a perfect, is at least a more accurate pa pe than 
has hitherto been presented. 
THRACIA PUBESCENS. 
Th. test ovato-oblongá, subventricosà, inequivalvi, subequilaterali, 
cinereo-albescente, anticé rotundatà, posticé subtruncata et angulata, 
bardina t LATE UR S $ E | hiti Sii + 
Inis 
Mya declivis, Penn. Brit. Zool. IV, No. 15, sed 
non M. declivis, Donov. 
Mya pubéscens, PurrENxv, in Hutch. Dors. Catal. 
27, tab. 4, f. 6. 
Mya (Ligula) pubéscéns, Mont. Test. Brit. p. 40. 
citatione Donovani exclus. 
Mya declivis, Maron and Racxert, Linn. Trans. 
VII. p. 36, citat. Donov. exclus. 
* 
