COEALLINE LIMESTONE. 



335 



CEPHALOPODA OF THE CORALLINE LIMESTONE. 



I find it necessary to place under this class the two following very remarkable species from 

 this rock. In their external form and general features they resemble Gasteropoda, but a careful 

 examination has satisfied me that they are septate. They are probably the earliest representatives 

 of spiral chambered shells. The chambered character does not appear to be accidental, or the 

 result of the animal gradually leaving the apex of the shell, as would appear to be true of 

 EuoMPHALtTs ; but a peristent character existing at all stages of growth. 



Genus TROCHOCERAS. 



Turbinate or trochiform ; spire elevated, more or less ventricose, umbilicated ; aperture 

 rounded or round-oval ; volutions above the outer one septate ; siphuncle submarginal or dorsal. 



In the specimen from which the generic description is principally made, the septa are 

 strongly arched from the inner basal angle of the volution to the outer one, advancing on the 

 outer angle towards the aperture. 



701. 1. TROCHOCERAS GEBHARDII* (n. sp.). 



PL. LXXVn. Fig. 2 ; and Pl. LXXVII A. Fig.la-d. 



Shell trochiform ; spire moderately elevated ; elevation, compared with width of base, about 

 as four to five ; umbilicus large and deep ; volutions in the upper part of the shell nearly 

 triangular, becoming oval and roundish towards the aperture, distinctly and rather prominently 

 angular on the inner edge ; septa highly arched on the base of the volutions ; siphuncle not 

 distinctly visible ; surface of the shell unknown. 



I have before me two specimens of this shell, one of which is represented on Plate 77. fig, 2. 

 In this one the upper part of the shell is still adhering to the compact limestone ; the two last 

 volutions are free, and the umbilicus is open nearly to the apex of the shell. The umbilicus 

 measures three inches in depth, and two and a half inches in diameter across the base. A con- 

 siderable part of the last volution has been broken off from the aperture upwards. As nearly as 

 can be ascertained, both from this and another specimen, nearly the whole of the last volution 

 is free from septa, and corresponds to the outer chamber of other cephalopods. On removing 



* I take pleasure in dedicating this remarkable and peculiar species to my friend John Gebhard junior, whose 

 untiring labors during the past eighteen years have done so much in the development of the geology and palaeontology 

 of his own county, and by whose labors Schoharie has been made classic ground. But for the zeal and persistent 

 labor bestowed by JMr. Gebhard on the rocks of Schoharie, it would have bee» impossible for me, with the time 

 and means at my disposal, to have procured the many beautiful and unique specimens which have been kindly 

 loaned to me by their owner for use in this work, a large part of which will appeal in the succeeding volume. 



