138 THE NAUTILUS. 



A NEW SPECIES OF MODIOLARIA FROM BERING SEA. 



BY WILLIAM HEALY BALL. 



Iredale has selected as type of Musculus Bolten, 1798, the 

 species Mytilus discors Gmelin, the Musculus of Klein having no 

 nomenclatorial standing. Therefore the familiar name Modio- 

 laria becomes a synonym. 



In a handful of dry algae sent from the Pribiloff Islands, 

 Bering Sea, by Mr. G. Dallas Hanna, and profusely in- 

 habited by the fry of Mytilus edulis, Turtonia minuta and young 

 Haloconcha reflexa, a number of specimens which seemed un- 

 duly inflated for young Mytilus were noted. Placed under the 

 microscope these were recognized as something new, though a 

 casual glance would hardly have led to their separation. 



Musculus phenax n. sp. 



Shell small, very solid, inflated, brownish or bluish black, 

 mytiliform; anterior end very short, but with the beaks extend- 

 ing slightly in front, attenuated, rounded, compressed below, 

 with two or three radial impressed sulci; posterior end widen- 

 ing, rounded, the dorsal margin with an obscure angle about 

 midway, the base behind the sulci convexly arcuate; the beaks 

 blunt, inflated, conspicuous; surface polished, with inconspicu- 

 ous incremental irregularities; interior blackish purple, with a 

 very strong nymph for the ligament, and three or four denticles 

 where the external sulci meet the margin. Length 7.7, maxi- 

 mum breadth 4.5, maximum diameter 4.0 mm. 



Habitat. St. George Island, Pribiloff group, Bering Sea, 

 living among algae, to which the specimens adhere by a strong 

 byssus. U. S. Nat. Mus., no. 271733. 



This would certainly be taken for a young Mytilus without 

 careful examination. The most obvious differences are the 

 greater inflation; the anterior portion (which is usually pale in 

 the Mytilus) is dark; the inflated beaks which do not quite 

 reach the anterior end, and internally the hinge characters. It 

 agrees with M. vernicosa Midd. in not forming a byssal net over 

 the valves. 



