MYTILLUS HAMATUS. 



Longitudinally grooved ; incurved at base. 



SYNONYM. 



M. HAMATus. Nob. Journ. Acad. Nat. Sc. Vol. 2. p. 265. 



M. STRiATus, ^arwe«. 



DESCRIPTION. 



Shell at base incurved and acute ; valves on every part 

 of the exterior with longitudinal, elevated lines, which are 

 bifid and sometimes trifid towards the tip, and transversely 

 striated with numerous small equal lines ; colour blackish- 

 brown with an olivaceous reflection ; within dark purpur- 

 escent, subiridescent ; margin crenate, whitish. 



OBSERVATIONS. 



- A very common species in the Gulf of Mexico, and is 

 carried to the New Orleans market in consequence of its 

 parasitical attachment to the common oyster. Hardly a 

 cluster of oysters can there be found unaccompanied by 

 one or more and generally numerous specimens of this 

 shell, in various stages of growth. Our figure represents 

 a fine large specimen, in which the incurved tip is not so 

 remarkable as in many smaller individuals, and the form 

 is somewhat more elongated and less triangular. It seem? 

 to approach M. decussatus as described by Lamarck, but 



