LOWER IIELDERBERG ROCKS. 
123 
Fig. 15. The exterior of the base of an individual of this species. 
Fig. 16. The interior of the same. 
Fig. 17. Profile or lateral view of the same. 
Fig. 18. The interior of a large specimen. 
Geological position and locality. In the upper part of the shaly limestone of the 
Lower Helderberg group, and in the “ Scutella limestone ” : Helderberg mountains, 
and Schoharie. 
Aspidociiims callosus (n. s.). 
Plate Y. Fig. 13 & 14. 
Base small, rounded below, somewhat quadrangular and much thickened 
above ; having prominent rounded points or nodes, with narrow spaces 
between. 
This form bears as much analogy to the root as to the calyx of a crinoid, and may 
perhaps be only this part of the individual. Other similar forms exhibit a variable 
number of thickened marginal nodes; although there is no appearance of small 
rootlets, as is usual, and the point of attachment for the column is quite small. 
Fig. 18 & 18. Interior and exterior views of the specimen described. 
Geological position and locality. In the shaly limestone of the Lower Helderberg 
group : Helderberg mountains, and Schoharie. 
Aspidociiims digitate (n. s.). 
Plate V. Fig. 19 & 20. 
The specimen figured has, in some respects, so much the character of a root, that 
it is not easy to suppose it to have been anything else; but the mode of attachment 
of the column is precisely as in the calyx of a crinoid, and entirely unlike ordinary 
roots of these fossils. The divisions terminate abruptly, without any evidence of 
prolonged rootlets, or of any mode of attachment whatever upon the lower side. 
Fig. 19 & 20. Upper side and profile view of the specimen. 
Geological position and locality. In the shaly limestone of the Lower Helderberg 
group, Schoharie. 
