LAMKLLIBRANCHIATA. 67 



curved, dorsal side risscu in the middle and compressed, with the rather tumid and i^rominent umboiies 

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

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

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

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

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

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

 Length up to 17.5 """. 



At West Greenland Modiolaria faba has been taken as far south as at Ivigtut (6i°i3' N. 1^.); 

 it first appears in quantit}' at Godthaab (64''ii' N. I^.) and it is counnou further north, at least up to 

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

 chiefly on stony, algae-covered clay bottom. — In Umanak F~jord I have found it attached by its 

 byssns 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 Havuefjord in Jones Sound (Grieg), Cumberland Soimd on 

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

 Bush and DalP). 



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 for two-thirds of its 

 extent; the jDosterior 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. IcBvigata; extended whitish, contracted brownish, in \-oung specimens yellowish." 



MoUer 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." 



■) Morch's record of its occurrence at the coasts of Denmark must be based on a mistake, as C. G. Joh. Petersen 

 has already remarked i^Om de skalb. MoUuskers Udbredningsforhold, 1888, p. 128), as also Beck's statement that itlives at Iceland. 



9* 



