INVERTEBRATES. 297 



MOLLUSC A. 

 BRACHIOPODA. 



Genus PRODUCTUS, Sowerby, 1812. 



(Min. Conch., i, p. 153.) 



Prodtjctus parvus, M. and "W. 



PI. 23, figs. 4a, 4b, 4c, 4d. 4e. 



Productus parvus, Meek and Worthen, October, 1860. Proceedings Acad. Nat. Sci., 

 Philad., p. 450. 



Shell rather small, nearly hemispherical, without any traces 

 of a mesial sinus; length and breadth about equal; hinge 

 equaling the greatest breadth; front rounded; sides intexsect- 

 ing the ears nearly at right angles, sometimes slightly sinuous 

 near the hinge. Ventral valve gibbous, regularly arched, not 

 depressed in the visceral region; beak incurved a little beyond 

 the hinge; ears small, moderately distinct from the swell of 

 the umbo, not flattened. Dorsal valve deeply concave, partic- 

 ularly in the middle and towards the beak. Surface of both 

 valves ornamented by numerous small, rounded, rather closely 

 arranged, occasionally bifurcating striae, about six of which 

 may be counted in the space of one-tenth of an inch Spines 

 small, erect, apparently confined to the ventral valve, each ear 

 of which supports some seven or eight, while there are usually 

 about three times that number scattered around the lateral and 

 anterior slopes. Sometimes very obscure traces of small con- 

 centric wrinkles are indistintly visible near the beak and on 

 the ears, particularly of the ventral valve. Length, 0.54 

 inch; breadth, 0.55 inch; convexity, 0.38 inch. 



This species might be mistaken, at a first glance, for P. elegans, of Norwood 

 and Pratten. On comparison, however, it will be found much less produced 

 in front, while the convex part of its ventral valve is not so attenuated towards 



38 Sept. 18, 1866. 



