Mineralogy and Geolegy. 275 
The occurrence of the C. Logani in the Tully limestone carries back 
the appearance of this species to a much earlier epoch than had hereto- 
fore been known. The species is not known in the Chemung group 
within the State; though found in the sandstones of the same in 
Ohio, and in the beds at the base of the Burlington limestone in lowa- 
and Illinois. 
In the Chemung group we have the recurrence of Chonetes scitula, 
C. lepida and C. setigera ; with a new and remarkable species, the C. 
muricata, which has the apex truncated and the surface of the ventral 
valve ornamented with spines, but having the vascular markings peculiar 
to the genus. 
Under the head of Productus and Strophalosia, the relations of these 
genera and of the genus Aulosteges are discussed. The Devonian species, 
The subgenus Productella is compared as follows, in Pal. N. Y., vol. 
IV, page 153: “These shells differ from Strophalosia in the extremely 
arrow linear cardinal area, greater extension of the hinge-line, more 
ce of an area, hinge-teeth and sockets. : . 7 
_ The Productellze of the Upper Helderberg and Hamilton groups men- 
tioned are, P. subaculeata, navicella, Shumardiana, spinulicosta, trun- 
ata, dumosa, ezanthemata, Tullia (n. 8.), subalata ; of the Chemung 
Stoup, P. hirsuta, hirsuta var. rectispina, r é lachrymosa, 
lackrymosa var. linea, lachrymosa var. stigmata, speciosa, striatulata (n.s.), 
ystriculata, (n. s.), costatula (n. s.), costatula var. sirigata, arctirosirata, 
bialveata (n. .), onusta (n. 8.). 
some species of Productus, Jt differs from Productus in the constant 
3 ” 
