LAMELLIBRANCHIATA. 



57 



'•Idas argenfats is probably the species of that name noticed by Verrill as xar. laiiirllo.sa", and the 

 added knowledge of l(f(7s a/or/z/r/ts o1)tained in that year really disposed of the pcctdiaritics of 

 \' err ill's /(/tis. 



Modiolaria. 



The 4 northern species of this genus may, according to my experience, most readily be dis- 

 tinguished from one another iu the following manner: 



The shell 

 radially 

 striated 



over the whole M.faba. 



not distinctly separated M. nigra. 



only on anterior 

 or also on the 

 posterior area. 



Central 

 and poster- 

 ior areas of 

 shell 



separated 

 by a dia- 

 o-onal fur- 



Central 

 area 



smooth M. discors 



(cum var. lavigata et subsfriata). 

 shagreen-like wrinkled M. corrugafa. 



Modiolaria discors Linne. 

 The true Modiolaria discors Linne does not occur at Greenland, Jan Mayen or Iceland. The 

 species is represented here by "Modiolaria Icevigata Gray" and "Modiolaria suhstriata Gray", which I 

 do not consider separate species, but varieties of a species which also embraces "Modiolaria discors 

 Linne". The last name has the prior right by age and must consequently have the advantage in 

 the designation of the species. 



var. Icrvigata G r a y. 

 PI. in, fig.s.4a— b. 



Modiola Iccvigafa Gray, Parry's first voyage, Suppl. to App., 1824, p. 244. — Crenclla lavigata 

 T o r e 1 1, Spitsbergens Mollu-skfauna, 1859, p. 133. — Modiolaria discors Gould & 

 Binney, Rep. Invert. Mass., 1870, p. 192, fig. 489. — Modiolaria Iccvigata Sars, Moll. Reg. 

 Arct. Norv., 1878, p. 29, PI. 3, fig. 3; Leche, Vega-Exped. Veteusk. Arb. Ill, 1883, P- 45°! P'- 34i 

 figs. 27—28. 



Alytikts discors Fabricius, Fauna groenl., 1780, p. 418. — Mytilus discors^ arciicus Fabricius (partim), 

 K. D. Vidensk. Selsk. Skr. 1788, p. 453, figs, i & 4 — 6. — Modiola discors Moller, Index 

 Moll. Groenl., 1842, p. 19. — Modiolaria discors Beck, in Gaimard, Voyage de la Recherche, 

 PI. 17, fig. 2a— h. — Modiolaria Icrvis Beck, ibid. PL 17, fig. 3f. — Modiola discors Beck, 

 Amtl. Bericht 24. Versamml. deutsch. Naturf. in Kiel, 1847, P- ^^S- ~ Modiolaria Iwvigata 

 Morch, Rink's Gronland, 1857, p. 94; Vidensk. Medd. Naturh. Foren. 1868, p. 224; Arctic 

 Manual, 1875, p. 133; Rink's Dan. Greenland, 1877, p. 442; Bee her, Osterr. Polarst. Jan 

 Mayen IH, 1886, p. 69; Posselt, Medd. om Gronland, XIX, 1895, p. 67; ibid. XXIII, 1898, 

 p. 25; Jensen, ibid. XXIX, 1909, p. 326. — Modiolaria cor ruga la (non St imps on) et Icevigata 

 Hagg, Ark. for Zoologi, Bd. 2, No. 2, 1904, p. 22 & 23. 



The Ingolf-Expcdition. II. j. 8 



