I. VMELLIBRANCHIATA. 





curved, dorsal side rissen in the middle and compressed, with the rather tumid and prominent umbones 

 lying at the front end. The valves fairly thin but strong, with a brownish or yellowish, somewhat 

 iridescent periostracum and provided over the whole with distinct, flatly rounded ribs, which to a 

 number of ca. 50 radiate out from the umbones towards the circumference of the shell and are of the 

 same breadth as or little broader than the intercostal furrows, but broadest towards the anterior end; 

 the circular lines of growth very fine. Interior iridescent, usually pale-reddish or violet, creuulated at 

 the margin; a crenulation of ca. 7 small teeth on the hinge-plate under and in trout of the beak. 

 Length up to 17.5 mm . 



At West Greenland Modiolaria faba has been taken as far south as at Ivigtut 161 13' X. I,.i: 

 it first appears in quantity at Godthaab (64 "u'X.L.) and it is common further north, at least up to 

 Melville Bay. It is met with most frequently in shallow water (o — 15 fm., more seldom 20 — 30 fm.) ami 

 chiefly on stony, algae-covered clay bottom. -- In Umanak Fjord I have found it attached by its 

 byssus to sea-weed, which floated at the surface over very great depths. 



Distribution. Elsewhere the species is only known on the American side, namely: Cape Sabine 

 in Smith Sound (78°45' N. L.), 2— 5 fm. and Havnefjord in Jones Sound (Grieg), Cumberland Sound 011 

 Baffin Land (Dall, Pfeffer), as also from Labrador southwards to 5i°33'X.L, o— 15 fm. (Packard, 

 Bush and Dall 1 ). 



Remarks. The numerous specimens at my disposal from Greenland show, that the form is 

 variable to some extent, sometimes swollen and low, sometimes comparatively flat and high; to make 

 this evident I have taken the measurements of the following specimens: 



In a manuscript left by the author of the Index Moll. Groenlandiae, H. P. C. M oiler, the following 



information is given regarding the animal: "The mantle is open in front tor two-thirds of its 



extent; the posterior third is closed and forms a short conical tube, broad at the base. The hindmost 



part of the open mantle may extend a little out over the margin of the shell. The foot, when quite 



extended, is twice as long as the greatest length of the shell, otherwise quite similar in form to the 



foot in M.lamgata; extended whitish, contracted brownish, in young specimens yellowish." 



Moller writes further on M.faba: "The colour of the shell is dark chestnut-brown; the quite 



small specimens are clear lilac; those I have taken here in deep water and in the open sea, were 



greenish and very light-coloured .... It occurs on Laminaria in great quantity at Godthaab and 



further north along the coast; but I have also obtained it at a depth of 30 fm., 8 Danish miles from 



the coast." 



■) Moreh's record of its occurrence at the coasts oi Denmarl must 1" based on a mistake, .i> C. G.Joh. Petersen 

 has already remarked (Om de skalb Molluskers Udbredningsforhold, [888, p. 1 iS , a also Beck 1 av at thai it Hi 



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