214 
PALEONTOLOGY OF NEW YORK. 
tion about the right and lower edges of the specimen. Sixteen of these 
spines may he counted, the first eleven lying regularly one below another 
along the edge of the terminal and first right lateral plates, and increasing 
in size downward. The remaining five are larger and detached, but still 
showing a degree of order in their arrangement, their bases all directed inward 
about the lower margins of the specimen. These spines are about four times 
as long as wide, the first ten deeply grooved on their exposed surface, the last 
six apparently turned over, showing a surface sharply carinate on the axial 
line and grooved within the margins. The position of this range of spines 
was in all probability opposite to the axial range of small plates, and the 
pressure, to which the specimen has been subjected in the shale, has displaced 
it by pushing it around to the right without scattering the spines to any 
great degree. 
The plates and spines are calcareous, with a strongly punctate surface, and 
more or less distinct concentric growth-lines, which in the broader plates are 
crossed by low, radiating ridges and furrows. The basal edges of the plates 
are thick and crenulated on the under side. 
The species thus appears to have been composed of four vertical ranges, 
three of plates and one of spines; of these the two larger rows of plates 
were in themselves asymmetrical, but were symmetrical in position, number 
and form; the third row was made up of bilaterally symmetrical plates, 
themselves symmetrical in position with the row of spines. All these 
ranges overlapped or were terminated by a conical plate. 
Dimensions. The terminal plate has a diameter of 10 mm., and a height 
of 5 mm.; the elevation of the apex is slightly more than this in some of 
the other plates, and the width of the plates in the lateral ranges varies as 
pointed out in the description. The smaller plates have a diameter of 4 or 
5 mm. ; the spines a length of from 5 to 8 mm. The entire animal must 
have been between 25 and 30 mm. in length. 
Observations. In the species of Turrilepas (T. Wrightianus), figured by H. Wood¬ 
ward (Quarterly Journal Geol. Soc., vol. xxi, 1865), and of Plumiilites given by 
Barrande (Syst. Sil. de la Boheme, vol. i, suppL, 1872), the number of vertical 
