﻿NORWOOD AND PRATTEN ON PRODUCTI. 17 



Section V. 

 PKODUCTI SPINOSI. 



P. Villiersi, A. d'Orbigny. — De Koninck " On the Genus Procluctus." PI. XL, 

 fig. 1. 



Locality. — Keg Creek, Missouri. Illinois State Collection. 



P. scabriculus, Martin sp. — De Koninck " On the Genus Procluctus." Plate XI., 

 fig. 6. 



Geological Position and Locality. — This fossil is found generally distributed in the 

 limestones of the coal measures. It is also met with in the mountain limestone at 

 Paris, Missouri. Illinois State Collection. 



P. Prattenianus, nob. — PI. I., fig. 10, a, b, c, d. 



Shell of medium size, transverse. When placed on its ventral valve, presents a 

 rectangular form. Cardinal line equal to the greatest breadth of the shell. The ears 

 are much extended, and garnished with a double row of tubes, very large in propor- 

 tion to the size of the shell; those nearest the cardinal border being directed back- 

 wards, and projecting far beyond the edge, while those in the second rank point im- 

 mediately upwards. The ears are covered with large folds. On the visceral portion 

 a few irregular undulations occur, none of which traverse it entirely. Dorsal valve 

 tolerably regularly arched ; its anterior part flattened, sometimes depressed in the 

 middle, and then showing a wide, shallow sinus. The sides slope very gradually 

 down to the ears. The beak is small, rather pointed, and passes the cardinal border. 

 The surface is covered with a great number of longitudinal ribs, regular in form, and 

 increasing by the implantation of new ones. From twenty to thirty tubes are 

 scattered over the surface ; the remains of which show them to have been very long 

 in proportion to the size of the shell. They all project from the shell at nearly right 

 angles to their attachment, but, after proceeding a short distance, bend downwards- 

 The anterior prolongment is broken off on every specimen in our possession, with the 

 exception of a small fragment on the flank of one. This fragment passes about ten 

 millimetres beyond the visceral disk of the ventral valve. 



Ventral valve concave, the visceral disk being divided from the ears by a very 

 large fold, with a deep hollow between this fold and the cardinal border. On this 

 valve there are neither tubercles nor hollows ; its ribs are like those of the dorsal 

 valve. Outside of the visceral disk the shell is traversed by three or four wide 

 imbricated folds. On the interior of the ventral valve there is a small bifid tooth, 

 with a rounded hollow at its base, from which projects a very slender ridge, which 

 crosses about one third of the valve. 



Dimensions. — Length, 20 millimetres. Comparison. — Length, 100 ; breadth, 130; 

 thickness, 0.35. 



