272 GINGLYMACONCHA, MYADZ. 
and slightly covering the left; epidermis extremely thin ; pro- 
cess bearing the opening ligament in both valves spoonshaped. 
GALAXURA PRETENUIS. 
Shell smooth, striated concentrically; the inferior strie, 
especially anteriorly, elevated ; gradually narrower behind ; its 
extremity rounded and finely granulated. Length an inch and 
four-fifths ; height an inch. 
Mya preetenuis, Pult. Cat. Dorset. 28.t.iv.f. 7; Mont. Test. 
Brit.41; M. & R. Trans. Linn. Soc. vin. 37 ; Dill. Desc. 
Cat. 43; Turt. Conch. Dict. 101. 
Ligula pretenuis, Mont. Test. Brit. Suppl. 23; Flem. 
Edinb. Encycl. vi. 88. 
Inhabits the shores of Devon and Cornwall. Length 13; 
height 1 inch. 
Genus 20. [xartta. 
Shells convex and subventricose ; umbones situated behind 
the middle of the back ; nearly equally large ; the epidermis 
thin; the process bearmg the opening ligament in both valves 
connected posteriorly with the shell; a triangular excavation 
for the ligaments. 
IXARTIA DISTORTA. 
Shells dirty white, concentrically striated with antiquated 
striee, narrower behind and rounded, and generally more or less 
distorted. Length one inch; height six lines. 
Mya distorta, Mont. Test. Brit. i. 42. t. i. f. 1; M.& R. 
Trans. Linn. Soc. vii. 37; Dill. Dese. Cat. 45; Turt. 
Conch. Dict. 101. 
Ligula distorta, Mont. Test. Brit. Suppl. 23; Flem. Edinb. 
Encycl. vi. 88. 
This species is extremely common on the western coast of 
England, especially at Falmouth, where it is found burrowed 
in limestone, and is therefore consequently more or less dis- 
torted. The most common distortion is in having the inferior 
margin of the shell undulated. 
