17 



FRODUCTUS hon-idus. 

 TAB. CCCXIX.— Fig. 1. 



Spec. Char. Quadrangular, with a large fur- 

 row along the middle, eared, thorny; ears 

 prominent, subcylindrical ; beak much in- 

 curved, large. 



J- HE spines are scattered all over the surface upon ob- 

 scure ridges, are large and rather numerous, those upon 

 the ears are placed in rows and are particularly strong : 

 the surface of the larger valve is so much curved, that 

 the ears appear to project from the mitidle of the sides ; 

 they are rather large, convex above and concave beneath ; 

 both sides have spines ; the lesser valve is very concave- 

 Not very rare in Derbyshire, communicated by Mr. 

 White Watson, from the seventh bed of his first Lime- 

 stone, probably Magnesian, as it is above the Coal 

 series. 



PRODUCTUS sulcatus. 

 TAB. CCCXIX.— Fig. 2. 



^Spec. Char. Semicylindrical, short, convex 

 above, with a concave space along the 

 middle; spinose? coarsely sulcated ; hinge 

 line as long as the shell is wide. 



J. HE concave space along the middle, and the distance 

 of the furrows from each other, distinguish this from 



