328 Dr. Maton’s Description of 
of Mya variabilis is the radiating ruge, or plaits, which proceed 
. from the apex of the umbones, and cover nearly the whole of the 
shell. ‘This circumstance, added to some others, induced me, at 
first, to look upon this shell as a variety of Mya corrugata, of 
Müller ( Hist. Verm. terr. et fluv. 2. p. 214. n. 398), but, on con- 
sulting the figures of that species given in the Beschaft des Gesell. 
Naturf. Freunde zu Berlin, (tom. 4. p. 35. tab. 3. f. 7. 8), and by 
Schröter ( Flussconch. n. 182. tab. 9. f. 3), lat length decided to 
the contrary, its habit being totally different, though, from the 
ambiguity of the description given in Gmelin, I might have 
made a very gross mistake, had I been unable to consult the au- 
thors just mentioned. In fig. 6 of the plate annexed to this 
paper, it will be seen that the ruge, though so strong over the 
whole of the younger shell (fig. 5), are very indistinct as they 
pass towards the margin, and in fig. 4, the oldest of the three 
specimens, they are almost obsolete, except on the decorticated 
umbo : it will be remarked also, that the outline of the shell be- 
comes totally different at its full growth, gradually verging from 
a subrhomboidal, or somewhat obliquely oval, to a subrhombic 
or almost orbicular form. As these differences are so marked, no 
person, I conceive, who duly considers the facts which I have 
mentioned, will be liable to separate Mya variabilis into several 
species. | 
3. TELLINA LIMOSA. 
Tas. XXIV. Fig. 8, 9, 10. 
. TeLtınAa testa zquivalvi, ovata, transversim striata, intus pur- 
purea, umbonibus acutiusculis prominentibus. 
Habitat in America australi, fluviatilis. 
Testa vix deos glabra, epidermide viridi, margine uS: 
$ pollicis longa, $ pollicis lata. 
Fig. 10. 
