1(3 



The specimen fii^. 5. is from Cloghran in the couiify 

 of Dublin, and was give^i me by Mr. Joseph Hum- 

 phreys. Fig-. 6 is from Derbyshire, through the kind- 

 ness of the late Mr. Salt; it is by no means an uncom- 

 mon shell in the Mountain Limestone. I have quoted 

 Martin's figures with a doubt, because my specimens 

 are not enough reticulated to agree with thein, though 

 they are probably only varieties of his semireticiilatus, 



PR0DUCTU8 concinnus. 

 TAB. CCCXYllL— Fig. I. 

 Spec. Char. Semicylindrical, convex above, 

 with a concave front and narrow back, 

 neatly striated and spinous ; lesser valve 

 flat, deeply inserted. 



J\. POLISHED, thin, evenly made shell, much resem- 

 bling P. Martini, but smaller and smoother. 



Found in very dark brown Limestone in Derbyshire 

 and near Richmond in Yorkshire. The flat space 

 around the edge of the lower valve occurs also in P. 

 Martini, as Mr. Martin's excellent figure sitews, but it 

 does not appear to be constant. 



PRODUCTUS lobatus. 

 TAB. CCCXY III.— Figs. 2 to 6. 

 Spec Char. Bilobed, very convex, furrowed, 

 and spinous ; spines few. 



In general form much like P. Martini, but divided 

 into two lobes by a deep cavity along the front ex- 

 tending to the beak : the sulci or deep strise are few, 

 and the hinge as long as the shell is wide, which is 

 seldom three-quarters of an inch. 



Fig. 2 exhibits two views of a specimen, in which 

 the shell is almost rotten ; it is from the same locality 

 as the following. 



Figs. 3 and 4 are remarkably elongated : they are 

 from a kind of Marie, probably decomposed Limestone, 

 that occurs in Well Houses farm, belonging to the Rt, 

 Hon. and Rev. Lord Charles Annesly, at his seat 

 called Little Park Tower, in Northumberland, and are 

 accompanied by P. Concinnus. 



Fi"". 5 is in Limestone ; it was collected by Dr. 

 W. E. Leach on the Island of Arran. 



Fi«-. 6 is from a cast in Sandstone, and shews the 

 bases of four spines very regularly placed : it is from 

 Cuu>berland. 



1 have this species also frogj Derbyshire. 



