PELECYPODA. 865 



has only a single riblet twisted in under the umbo. Ligament long 

 and carried in a channel beneath the umbones. Hinge without definite 

 teeth, but having a tooth-like ridge in one valve which fits into a groove 

 or depression on the other valve. Anterior adductor often absent, but 

 other scars as in Eumytilus. 



3. Mytilus magellanicus, Lamarck, 1819. Plate 56, fig. 6. 



Mytilus magellanicus, Chemnitz, Conch. Cab., viii, pi. 83, f. 742 ; not 



binomial : Lamarck, A.s.V., vi, 1819, 119 ; Conch. Icon., x, pi. 6, f. 22 ; 

 - Hanley, Cat. Rec. Biv. Shells, 244 ; M.N.Z.M., 166 ; E. A. Smith, Chall. 



Rep., xiii, 272 ; Chenu, Man. Conch., ii, 152, f. 746 ; Pelseneer, Voy. 



" Belgica," 10 ; Melvill and Standen, Scot. Antarct. Exp., 145. M. polyo- 



dontes, Q. & G. : Gray, Dieff. N.Z., 259 ; not of Quoy and Gaimard. 



M. capensis, Dunker, in Menke's Zeitschr. f. Malak., 1846, 108. 



M. crenatus, Lamarck: Krauss, die Siidafrik. Moll., 1848. 24; not of 



Lamarck. 



Shell not very large, oblong, subtrigonal. distinctly angled, thick. 

 longitudinally ribbed, black. Beaks acute, slightly curved, rather close 

 together ; in young specimens the partly smooth embryonic shell can 

 distinctly be seen. Anterior end pointed, inflated, the dorsal margin 

 ascending straight to the middle of the length, whence it is slowly 

 descending Posterior end somewhat compressed, regularly rounded ; 

 basal margin straight or slightly concave. Sculpture consisting of thick 

 raised undulating ribs, bifurcating toward the margins, and crossed by 

 concentric lines and ridges, which render the ribs more or less granu- 

 lose. Epidermis thick, brown or black. Colour white at the beaks, 

 the remainder purplish-black or maroon. Interior purplish-white, or 

 white, iridescent. Margins crenated or smooth. Hinge-plate small 

 and short, with ridge and groove. Ligament external, but deep-seated, 

 and with an upper channel, the sides of which are grooved. The 

 anterior adductor-scar is usually present, small and oval ; the posterior 

 adductor-scar is large, oval and united with the byssus-scars. Pallia], 

 line simple. 



Diameter Ant. -post., 82 mm. ; dorso-ventral, 42 mm. : thickness, 

 32 mm. 



Anatomy. Alex. Purdie, as quoted for M. edulis. 



Type in the Mus. Hist. Nat., Geneva. 



Hob. Rare on the shores of the North Island, but more common 

 south of Cook Strait. Chatham, Auckland, and Campbell Islands. 



The species is circumaustral. Recorded from the Fiji Islands, 

 Kerguelen Island, South Africa, Falkland Islands, Tierra del Fuegia, 

 Patagonia east and west, Chile, Peru. 



Fossil in the Miocene and Pliocene. 



Genus 2. MODIOLUS, Lamarck, 1799. 



Modiolus, Lamarck, Mem. Soc. Hist. Nat., Paris, 1799, 87. Type : Mytilus 

 modiolus, L. Modiola, Lamarck, Syst. A.s.V., 1801, 113; Jukes- 

 Browne, P. Mai. S., vi, 218. 



Shell oblong or elongate, oblique, generally inflated toward the 

 anterior side, and often compressed on the posterior side. Smooth 



28-Moll. N.Z. 



