78 LAMELLIBEANCHIATA. 



pressions and a band round the margin blackish blue ; three or four 

 small teeth in the left valve and one in the right. Height, 1'6 ; 

 length, 3. 



Common in the South, not so common in the North. Great 

 Barrier Island. Australia. 



* 99. HI. latllS, Lamark, I.e., vii., p. 41. Shell elongately ovate, 

 concentrically irregularly striated ; olive decussated with rays of bright 

 green beneath a thin horny epidermis ; posterior side straight, obtusely 

 slanting; anterior arched, scarcely angled. (Reeve.) 



100. M. ater, Zelebor, Seise Novara, Moll., pi. 2, ff. 29, 30. 

 Small, oblong, inflated, black, obsoletely concentrically striated ; broad 

 and obtuse iu front, rounded behind ; umbones tumid ; dorsal margin 

 much arched, straight behind ; lower margin sub-parallel. Blackish 

 blue, covered with a dark brown epidermis ; interior purplish, slightly 

 iridescent. Height, '5 ; length, 1. 



Common. 



CRENELLA. 



Short and tumid ; centre smooth and both ends ornamented with 

 radiating striae ; hinge margin crenulated behind the ligament ; in- 

 terior brilliantly nacreous. 



Temperate and Arctic seas. 



101. C. disCOPS, Lamark, vii., p. 23 ; Modiolacra impacta, Gray, 

 Dicff. N.Z., ii., p. 259. Oval, sub-diaphanous, the extremities radiately 

 ribbed, and the middle finely longitudinally striated. Brown, with 

 sometimes a mixture of green near the edge, inside highly iridescent. 

 Height, '85 ; length, T3. 



Common. Chatham Islands. Europe. North America. 



MODIOLA. 



Oblong, inflated in front ; umbones anterior, obtuse ; hinge tooth- 

 less ; pedal impressions three in each valve, the central elongated ; 

 epidermis often produced into long beard-like fringes. 



Warm seas. 



102. M. albiCOSta, Lamark, I.e., vii., p. 19. Smooth, swollen ; 

 covered with chestnut brown hairy epidermis, under which it is pink- 

 ish ; inside yellowish white, getting purplish behind. Height, 1 15 ; 

 length, 2. 



Common. Chatham Islands. Australia. 

 The Natives call this shell " purewha." 



103. M. SeCUriS, Lamark, I.e., vii., p. 22. Smooth, finely con- 

 centrically striated ; epidermis smooth, brownish black, under which it 

 is purple ; inside bluish white, purplish round the margin. Height, 

 '5 ; length, 1. 



Not so much arched as Mytilus ater. 



Great Lagoon, Chatham Islands. Australia and Timor. 



