GINGLYMACONCHA. MYADZ. ag 
** The process bearing the ligament irregular large. 
2. THRACIA DECLIVIS. 
Shell somewhat compressed, concentrically striated, sprinkled 
very closely with innumerable confluent granulations, truncated 
posteriorly, the lower angle rounded. Length nearly four 
inches ; height nearly two inches and a half. 
Mya declivis, Penn. Brit. Zool. iv.79 ; M. § R. Trans. Linn. 
Soc. vii. 36; Wood, Gen. Conch. i. 93. p. 18. f. 2, 3; 
Flem. Edinb. Encycl. vii. 88 ; Dill. Desc. Cat. 43. 
Mya pubescens, Mont. Test. Brit.40; Turt. Conch. Dict. 99. 
Inhabits all the sandy coasts of Britain in great plenty; the 
adult has been found only in very deep water on the western 
coasts : in these opposite states it has been described as two 
distinct species ; but I have seen such good series of the shell 
in every stage, as to satisfy me that the supposed species are 
but the young and adult of one animal. 
In the young state this species is whitish, and at first sight 
seems to be smooth; but when examined with a strong lens, 
its surface appears covered with very minute granulations, that 
are more distinct at the hinder part of the shell, which is 
always more or less tinted with dirty brown, or ferruginous of 
various tints. The process for the cartilage at this period wants 
the anterior border, which gradually increases during the growth 
of the shell, until it fills up a vacancy between the process and 
the umbo ; and at last forms a thick margin, connecting the 
process with the imner or lower part of the umbo. The adult 
shell is subpellucid, more or less tinted with dirty testaceous 
white. Length four inches ; height two inches and four-fifths. 
The right projects over the left umbo in the young, as well as 
in the adult shell. The inside is also silvery in the young 
state. 
Genus 19. GALAXURA. 
Shell with the left valve largest and most convex ; umbones 
situated behind the middle of the back, the right one largest 
