LlMELLTBftA^CHIATA. 77 



CARDITA. 



Oblong, inequilateral, thick ; hinge thick, with one or two very 

 unequal cardinal teeth, oblique behind, in each valve. 



* 93. C. tridentata, Say. Shell rather orbicular, nearly equi- 

 lateral, thick ; whitish, stained with rose colour and covered with a 

 thin yellowish epidermis ; longitudinal ribs two or three and twenty in 

 number, thickly ornamented with rude, rather nodulose, concentric 

 cross ridges, which do not penetrate into the interstices ; interior 

 white, sometimes tinged with rose colour. (Reeve.) 



FAMILY MYTILID.E. 



Equivalve, oval or elongated, closed, umbones anterior, epidermis 

 thick and dark, often filamentose ; ligament internal, sub-marginal, 

 very long ; hinge edentulous ; pallial line simple ; anterior muscular 

 impression small and narrow, posterior large, obscure. 



MYTILUS. 



Wedge-shaped, rounded behind ; umbones terminal, pointed ; hinge 

 teeth minute or obsolete ; pedal impressions two in each valve, small, 

 simple, close to the adductors. 



World-wide. 



94. M. magellaniCUS, Lanark, I.e., vii., p. 37. Oblong, sub- 

 trigonal, angled, uncinate, with thick longitudinal undulating granulose 

 ribs ; bluish or reddish purple, interior violet ; a single small tooth in 

 the right valve. Height, 1/65 ; length, 3. 



Common from Cook Strait southwards. Chatham Islands. South 

 America. 



* 95. M. polyodontes, Quoy, I.e., in., p. 462. Similar to the 

 last, but with eight or ten nearly equal teeth at the extremity of the 

 hinge. 



* 96. M. MrSUtUS, Lanark, I.e., vii., p. 38. Dark brown, 

 elevately radiately striated throughout, and clothed with a long fibrous 

 epidermis, the shafts of which are beset with small prickly spines. 

 Interior iridescent, green and purple. Length, 2'5. 



New Zealand (Gr. F. Angas). Australia. 



97. M. Smaragdinus, Chemnitz; M. smaragdinus et opalus, 

 Lanark, vii., p. 43 ; M. canaliculatus et latus, Martyn, nee M. lotus, 

 LamarJe. Oblong, beak obtuse, swollen, smooth, margin even ; covered 

 with an olivaceous brown epidermis, under which it is green varied 

 with chestnut brown ; margin green ; inside purplish white, iridescent, 

 hinge with one or two small teeth. Height, 3 ; length, 8'75. 



A very variable shell ; sometimes small specimens are bright green, 

 and sometimes pale yellow. 



Common. Found also in China. M. canaliculatus is found in the 

 Persian Gulf. 



98. M. dunkeTi, Reeve. Oblong oval, dilated and compressed 

 behind, umbones slightly uncinate ; covered with a dark olive brown 

 epidermis, below which it is blue; inside bluish white, muscular im- 



