37© 
PALAEONTOLOGY OF NEW-YORK. 
Surface granulose, the lobes of the glabella being unequally pustulose. 
This species usually occurs in fragments; a single specimen only preserving the 
parts in connection, and this one is too imperfect to afford the means of description. 
The description is drawn from isolated parts, which are represented on the plate. 
The fossil described by Mr. Conrad as Acidaspis tuberculatus was the central portion 
of the head, preserving the central posterior spine, while the separated cheeks were 
described as Acantholoma*. 
In certain slialy layers the fragments of this species are quite common, the 
separated cheeks being the most conspicuous parts. 
Fig. 1. View of a specimen preserving the members in connexion ; but the fossil being 
imbedded in a hard stone, the condition does not admit of the parts being shown 
in detail. 
Fig. 2. The central portion of the head, showing the lobes of the glabella, the frontal border, 
the occipital annulation, and the central posterior spine. 
Fig. 3. The central part of the head of another specimen. 
Fig. 4. Profile of the same. 
Fig. 5. A portion of the surface enlarged. 
Fig. 6 & 7. The right cheeks of two different individuals, preserving the eye tubercle, and 
showing differences in the exterior and inner spines. 
Fig. 8. The left cheek, which shows very distinctly, as do. the others, the gradation of the 
border ornaments, from small nodes at the anterior extremity, to distinct spines. 
Fig. 8 a. A cheek, with the eye tubercle, enlarged. 
Fig. 9 & 10. The underside of two cheeks, one of which shows a single spine on the inside, 
and the other a single spine with the rudiments of two others above it. 
Fig. 11. An articulation of the thorax. 
Fig. 12. The underside of a part of the thorax, showing the extension of the lateral spines 
of the articulations. 
Fig. 13. The pygidium, in which the upper lateral spine is not preserved. 
Fig. 14. The pygidium of another individual, showing the parts described. 
Geological position and localities. In the shaly limestone of the Lower Helderberg 
group : Albany and Schoharie counties. 
* Our knowledge of the Genus Acidaspis, at that period, was derived from the figures of some parts of 
the animal in Murchison’s Silurian System. These remarkable appendages did not correspond with any 
recognized parts of the Acidaspis, as known at that time. 
