JURASSIC FOSSILS. 49 



determine very exactly its outline, or as clearly as is desirable some of its other 

 characters. Its costse seem to he without nodes, hut it is possible that better speci 

 mens might show them to be faintly nodose or crenate. It seems not to be very 

 closely allied to any species with which I am acquainted. 



There are in the collection fragments of apparently two other species of this 

 genus. One of these is considerably larger than that described, and has the costae 

 distinctly nodose. They are, however, not angularly deflected, but curved gra 

 dually forward. 



FAMILY 



GENUS MYTILUS, Limueus, 1758. 

 MYTILUS MULTISTRIATUS, Meek. 



PI. 7, Fig. 7, and 7 a. 



SHELL narrow, subovate, arcuate, moderately convex; the 

 greatest convexity near the middle, or between it and the beaks ; 

 antero-ventral margin sloping backwards from the beaks, and a 

 little arched ; postero-basal extremity rather narrowly rounded ; 

 dorsal margin moderately arcuate, and passing rather gradually 

 into the sloping posterior border. Beaks curved a little, more or 

 less obtusely pointed, and not compressed. Surface with fine 

 regular radiating striae. 



Length from beaks to postero-basal margin, 1.23 inch; greatest 

 diameter at right angles to the same (below the middle), 0.55 inch ; 

 convexity, 0.36 inch. 



This species bears some resemblance to Mytilus pectinatus of Sowerby, from the 

 Kimmeridge clay ; but is less convex, and has less prominent anterior umbonal 

 slopes, while its radiating striae do not divaricate. Its beaks also appear to be 

 more pointed, and its postero-basal margin is more rounded. 



PAL. VOL. i. i 



