FEESHWATEE SHELLS OF AUSTRALIA. 301 



Lesson must have given him some specimens of his species pro- 

 bably before he had named it nepeanensis ; for had it belonged to 

 another species, we should expect to find it also mentioned in the 

 ' Voyage of the ' Coquille." The two descriptions display cer- 

 tain discrepancies, however ; but this is pardonable in so difficult 

 and variable a genus. Deshayes says it is subdepressed, brown- 

 green in the Latin diagnosis, and black-brown in the French 

 description, with a broad orange spot within ; hinge with three 

 very small cardinal teeth. 



On the other hand. Lesson describes the form as swollen, the 

 colour brownish fawn(" fauna bruuatre "), the interior rosy white 

 at the bottom, bluish on the margins, and the hinge possessing 

 two cardinal teeth. 



One character, not mentioned by either author, consists of two 

 purplish stains or rays which are seen in the interior, one on each 

 side beneath the lateral teeth. Still, allhough not referred to in 

 his description, Lesson depicts them, though feebly, in his figure. 



Prime* and Clessint appear to have erroneously united the 

 Cyrena australis of Deshayes with the Cyclas «Ms^r«/t> of Lamarck. 

 The Australian variety of the latter is, according to Lamarck, a 

 shell only 2 or 3 millim. in diameter. It belongs to the genus 

 Fisum. 



The species may be described as follows : — 



Shell subequilateral, transversely ovate, somewhat prominent at 

 the umboues, and compressed at the lateral and lower margin, 

 equally curved at both ends. Epidermis normally brownish straw- 

 colour, sometimes darker and olive-brown ; generally rather eroded 

 at the beaks, which are reddish and a little prominent beyond the 

 dorsal marginal curve. Concentric sculpture fine, becoming more 

 or less obsolete on the posterior side, where the epidermis exhi- 

 bits a less glossy appearance, and a number of very fine filaments 

 crossing the concentric strias obliquely. Ligament small, light 

 brown. Interior of the valves bluish white, somewhat reddish or 

 rosy towards the umbones, especially in young specimens, and 

 at times bluish or purplish towards the margins, besides which 

 there are two purplish stains or rays, varying in intensity in dif- 

 ferent specimens, one on each side beneath the lateral teeeth. 

 Hinge with a large double central cardinal tooth in the right 

 valve, with a deep triangular pit on each side of it, with a small 

 * Cat. Corbiculadse, Amer. Joiirn. Conch, t. Append, p. 128. 

 t Conch.-Cab. ed. 2, p. 140. 



