166 MYADA. 
characteristic form and appearance as in the so-called Lutraria 
oblonga and L. elliptica. 
M. arenaria, Linn. et Auctorum. 
M. arenaria, Brit. Moll. i. p. 168, pl. 10. f. 4, 5, 6. 
We have not observed this species, but the recorded ac- 
counts of it show that it differs little from the type. 
Having ventured to consider Panopea a superfluous genus, 
it 1s impossible that we can for a moment conscientiously 
maintain a still more unnecessary one, the “Lutraria” of 
authors; our description will show that the present animal is 
in all essential pomts a Mya; the differences of the specialties 
of the soft parts are scarcely worth notice, the cirrhi bemg 
red-brown instead of white, and the terminations of the 
siphons slightly forked, whilst in the type, the M. truncata, 
there is no separation. The greatest variation between the 
two is in the hard parts, but I trust, at the present epoch, we 
are not to adopt precepts of zoology which would be incom- 
patible with the present position of the sciences ; that because 
an animal shuts the door of its house by a different-shaped 
hinge from that of its congener in all other respects, it is to be 
considered, on that account, generically distinct: we may as 
well say of two similar doors, that because one has the patent 
hinges and the other the common sort, they are distinct kinds of 
objects ; it is the same with the M. oblonga: gentlemen may call 
its animal by the name of Lutraria, but that does not make it 
less a Mya. We maintain the position that there is not a 
trace of generic distinction between the typical Mya and the 
so-called L. oblonga and L. elliptica, and that there are no 
more decided specialties between them, than between the 
species of every other genus. Lutraria has not a malacolo- 
gical support; it entirely rests on the artificial grounds of 
variation of the dentition of the hinge; for the hgament or 
cartilage is what is called internal, both in Mya and Lutraria ; 
we therefore consider that an essential service is done in pro- 
posing to relieve science of a useless genus, which has not 
