nR4 



MANUAL OF THE MOLLUSCA. 



adductor scar central, near tlie umbo ; cardinal impressions 

 lateral, striated. 



Pig. 189. Productus giganteus, J Carb. limestone. 

 A, interior of dorsal valve ; B, interior of ventral valve, with tlie 'umbo removed; 

 C, ideal section of both valves ; D, hinge-line of A ; j, cardir.al process ; a, adductor* 

 r, cardinal muscles; b, oral processes?; s, hollows occupied by the spiral arms; v, 

 vascular impressions ; A, hinge-area. 



Peoductus, Sowerby. 



Types, P. giganteus, Martin. z=Anomia produda, Martin. 



Examples, P. horridus, PI. XV., Pig. 27. P. proboscideus, 

 PI. XV., Pig. 28. 



Shell free, auriculate, beak large and rounded ; spines scat- 

 tered ; hinge-area in each yalve linear, indistinct ; no hinge- 

 teeth ; cardinal process lobed, striated ; yascular impressions 

 simple, curved ; ventral valve deep, with two rounded or sub- 

 spiral cavities in front. These shells may have been attached 

 by a pedicle when young, the impressions of the pedicle-muscle 

 blending with those of the hinge-muscles (c) in the ventral 

 valve. A few species appear to have been permanently fixed. 

 P. striatus is irregular in its growth, elongated and tapering 

 towards the beak, and occurs in numbers packed closely together. 

 P. prohosddeus seems to have lived habitually in cavities, or 

 half-buried in mud, as suggested by M. D'Orbigny; its ventral 

 valve is prolonged several inches beyond the other, and has its 



