PALAEONTOLOGY OF NEW-YORK. 
im 
REMARKS ON THE GENERA PRODUCTUS AND STROPHALOSIA. 
Among the genera of the Family Production, there are recognized at 
the present time the following : Chonetes, Productus, Strophalosia and 
Aulosteges ; the two latter being considered by Mr. Davidson as sub¬ 
genera of Productus. 
The Genus Chonetes has already been noticed in the preceding pages; 
and from its marked characters, there is usually little danger of con¬ 
founding it with any other of the Productidse. The Genus Productus, in 
its typical and varied forms, is characteristic of the Carboniferous period : 
a few species are known in the Permian, while other similar forms in the 
Devonian, which were formerly considered as Ppoductus, have lately 
been referred to the genus or subgenus Strophalosia of Prof. King. 
Productus, which is the oldest established genus, includes species 
described as semicircular or semioval concavo-convex shells, with spini- 
feroiis exterior surface, straight hinge-line, without an area on either 
valve, and without teeth or sockets. The interior characters, though with 
a general resemblance to Strophodonta, have in addition certain other 
points by which they are distinguished. Notwithstanding that the spe¬ 
cies of Productus have usually the shell more or less closely studded 
with spines, and generally a row of spines just below the hinge-margin 
of the ventral valve, there are some species referred to this genus which 
are nearly destitute of spines, and others upon which no spines have 
been detected except on the ears or near the cardinal margin. Species 
having this exterior character are usually more extremely gibbous or 
ventricose in the ventral valve than any species of Leptnna, Stropho¬ 
donta or Chonetes, and the dorsal valve is more deeply concave. 
Strophalosia is described as differing externally from Productus in 
sometimes having a truncate apex, and by the presence of an area of 
greater or less extent on each valve, with a foramen which is more or 
less closed by a deltidium. In the interior, it is said to be characterized 
by teeth in the ventral valve and teeth-sockets in the opposite valve; 
