MYTILACF.A. 3I0LLUSCA. MODIOLA. 129 



MODI^OLA DI'SCREPANS. 



Shell Nuh-ovaf^ broadest behind; beaks nearly icrmirud; hinder 

 extremity somewhat lobed ; surface divided into three compart- 

 ments, of lohich the anterior is marked, by about eighty and the 

 posterior by wnnerowi radiating lines, epidermis olivaceous. 



Figure 83. 

 State Coll., No. 157. Soc. Cab., No. 2345. 



BIy'tilus (Iiscrepans, Montagu; Test. Brit., p. 1G9, and SuppL, 60. pi. 2(), f. 4. 



Maton and Rackett; Lin. Trans., viii. pi. '■^, f. 9. Pennant ; Brit. Zool., iv. 



241. Dillwvn; CafaL, 31!). Turton ; Biit. Biv., 202. Conch. Diet., \\2. 



Fleming ; Brit. Aniin., 41:?. Woon ; Index, pi. 12, f. 38. 

 My'tilus discors, U. Fabr. ; Fauna Grwnl., IHl. Chkmn. ; Conch., viii. 1!)I, 



t. 8(), f. 767. (var ) 

 Modiola lasvig\t:i, (var.) Gray; .^ppnulix to Parry' s 2d Voyage. 



Shell somewhat oval, rather oblique, highest about the middle, 

 rounded before, base slightly curved, hinge margin straight and 

 then curving obliquely downward ; beaks near the anterior end, 

 prominent, and rounded ; valves moderately convex ; surface 

 coarsely marked by the lines of gi'owth, and divided into three 

 fan-shaped compartments, of which the foremost one is marked 

 by about eight small, rounded, rib-like ridges, the spaces between 

 them being flat, the hinder one by numerous similar ridges, and 

 the central one is plain, or with very minute radiating lines ; the 

 limits between the posterior and middle compartments are desig- 

 nated by an elevated ridge passing from the beaks, and here the 

 basal margin of the posterior compartments projects abruptly be- 

 yond that of the middle one, so that the rounded point of the shell 

 forms a projecting lobe. Epidermis olive-green with dark chest- 

 nut-colored shades, folding over the edge. Interior of a brilliant 

 silvery lustre ; edge of the two extreme compartments crenulated, 

 and very strongly near the ligament ; a few folds on the edge, not 

 corresponding to the external ridges, are found just in front of the 

 ligament. Length 1 inch, height l^ inch, breadth /^ inch. 



Found on Chelsea Beach, and in fishes' maws. Larger speci- 

 mens are brought from the Newfoundland Banks. I have two 

 specimens which measure 1^ inch in length, ^ inch in breadth, 



17 



