MYTILACEA. MOLLUSCA. MODIOLA. 131 



Byssus very long. Length | inch, height T \ inch, breadth T 3 T 

 inch. 



Found adhering to the stalks of sea-weed (Laminaria), cast 

 upon the sea beach. 



The most obvious distinctive marks between this shell and M. dis- 

 crepans are, the more numerous anterior ribs, and the concentrically 

 corrugated epidermis. The shell is proportionally broader, the tip is 

 more pointed, more depressed, and forms a projecting lobe much like 

 that shell ; and the ribs are more decided. The shell is much smaller 

 and very much more rare. This is not M. discors of Lamarck, an 

 East Indian species. The M. discors of Turton (Brit. Biv., pi. 15, 

 f. 4.) seems to be a still different species, and I have received it from 

 Dr. Loven under the name of M. marmorata, Forbes. 



MODIOLA GLA'NDULA. 



Shell obliquely rounded-oval, regularly convex ; beaks small, 

 separate ; surface with minute lines of growth, crossed by minute 

 and crowded radiating lines ; epidermis brownish-yellow ; margin 

 crenulated. 



FIGURE 87. 

 State Coll., No. 160. Soc. Cab., No. 2346. 



Modlola glandula, TOTTEN ; Silliman's Journ., xxvi. 367, f. 3,e, f, g. 



Shell small, thin, rounded-oval, rather inflated, convexity 

 regular ; beaks small, rather prominent, curving, not in contact, 

 placed at about half the height of the shell ; anterior portion slightly 

 depending, base nearly straight, and the rest of the margin regu- 

 larly rounded ; surface with minute lines of growth, crosse'd by 

 very small, rounded, radiating ribs, about equal in size on all parts 

 of the shell, the number increasing as the spaces between them 

 widen ; epidermis thin, brownish-yellow ; within white, somewhat 

 pearly ; edges sharp and minutely crenulated, except the short 

 portion occupied by the ligament. Length -^ inch, height -/^ 

 inch, breadth ^ inch. 



This very pretty and singularly shaped Modlola was first found 

 by Colonel Totten, in Provincetown harbour. It is one of the 



