318 
PALAEONTOLOGY OF NEW YORK. 
The two species named are large, ponderous shells, having the cardinal area and 
teeth conspicuously developed, the external surface covered with fine radiating 
striae, and devoid of spines. The existence of the secondary muscular scar in 
the pedicle-valve can hardly be regarded as a distinctive feature, since it is also 
well defined in some other species of Productus. The form and size of the 
shells, the arrangement of the muscular scars, and their dendritic markings, 
and the structure of the cardinal process, all show the very close relationship 
of these species to the typical forms of Productus. It will be difficult to find 
features of intrinsic importance upon which to justify the separation of these 
fossils from Productella, unless it be in the spineless surface; and yet the 
general form and expression of the shells is so different from what we are 
accustomed to meet with in that distinctively Devonian genus, that for the sake 
of homogeneity in the grouping, it may be well to retain for them this desig¬ 
nation. 
Both P. Llangollensis and P. comoides are from the Welsh Coal Measures, and 
may be regarded as the final expression of that combination of characters con¬ 
stituting Productella in earlier faunas. 
