182 



COLPOCERAS VIRGATUM. 



Plate 5, fig. 2. 



Tube virgate, scarcely diminishing towards the apex ; surface strong- 

 ly annulated ; armulations arching towards the apex on the back of the 

 shell and bending downwards in an abrupt sinus on the ventral side, 

 and becoming almost entirely lost on the ventral line ; septa following 

 the direction of the annulations and arranged between them, except on 

 the ventral side where they encroach a little upon the annulation, being 

 more abruptly bent downwards ; septa in the longitudinal section, cut- 

 ting each side, regularly arched ; section when not compressed cylin- 

 drical ; siphuncle unknown ; character of the surface, except the annu- 

 lations, unknown. 



This species occurs near the junction of the Birdseye and Black river 

 limestones in Lewis county. 



ASAPHUS EXTANS. 

 Plate 3, fig. 1. 



Reference. — Asaphus extans. Palaeontology of New- York, vol. i., 

 page 228, plate 60, fig. 2, a, b, c. 



This species, which was described as an asaphus, with some doubt, 

 has again fallen under my observation, and though the specimens yet 

 procured are fragments, they throw some farther light upon the char- 

 acter of the fossil. These specimens are mostly in a bad state of pre- 

 servation, from a dark shaly layer near the base of the Trenton lime- 

 stone in Lowville. The character of the caudal shield which is preser- 

 ved in several specimens is well marked, though the rings of the thorax 

 attached are so much obliterated as to afford very little satisfactory evi- 

 dence of their number or character. Still there appears to be nine or 

 ten articulations of the thorax, though the junction with the caudal 

 shield is obscure. 



In connexion with a mutilated specimen, we have the convex middle 

 lobe of the cephalic shield, with two large and prominent eyes. This 

 specimen does not preserve the margin of the shield, but in another one 

 we find the two lateral portions of the shield preserved in their natural 

 relations to each other, the central lobe being wanting. This fragment 

 proves that the facial suture terminated on the base of the shield as in 

 asaphus, though it is difficult to reconcile the number of articulations of 

 the thorax with that genus. The prominent eyes are also like asaphus, 

 the form of the head is rather more prominent in the middle lobe than 



