SYNDOSMYA. 319 



S. INTERMEDIA, Tlioinpson. 

 Elongated, ovate, almost equilateral. 



Plate XVII. fig. 9, 10, and (Animal) Plate K, fig. 5. 



? Mya nitida, Muller, Prodr. No. 2963, (Not of 0. Fabric.) 



Amphidesma intermedia, Thompson, Ann. Nat. Hist. vol. xv. p. 318, pi. 19. f. 6. 



Ahra pro/undissima, (Young) Jeff. Ann. Nat. Hist. vol. xx. p, 19 (not of 



Forbes). 

 Syndosmya niiida, Loven, Index Moll. Skandinav. p. 44. 



It is by no means improbable that Muller intended to 

 indicate this graceful shell, under the name of il/y« nitida, 

 but as his description, which is unaccompanied by any 

 figure, so inadequately defines it, as to leave much room 

 for conjecture, we have preferred to retain the appellation 

 given by the distinguished naturalist who first introduced 

 it into our Fauna. 



The shell has an oblong, or rather elongated ovate-form, 

 and is of a brilliant porcelain white beneath the extremely 

 thin and almost imperceptible iridescent epidermidal sur- 

 face. It is subdiaphanous, exceedingly thin and fragile, 

 compressed, (particularly behind,) and almost entirely 

 smooth, or at most marked with indistinct striulai. The 

 anterior side, which is slightly but decidedly the more 

 produced, is rounded at its extremity, but not equally above 

 and below, since the front dorsal edge, which is barely con- 

 vex, slopes but little downwards, the rotundity being effected 

 by the ventral margin, which, although straight and some- 

 times almost subretuse in the middle, rapidly ascends at 

 either extremity and particularly and arcuatedly so in front. 

 The posterior side is attenuated to a more or less acute or 

 obtuse subcentral point ; the hinder dorsal edge, after pass- 

 ing the extremely short, small, and olivaceous ash-coloured 

 ligament (which scarcely projects,) slopes very moderately, 

 yet more so than the front one, to its termination, exhibit- 



