a08 PALEONTOLOGY OF NEW-YORK. 



Fig. 5. A fnipmcnt of tho pvgidium, where the posterior part of the axis is extremely pro- 

 minent, and the bases of the principal and smaller lateral spines are preserved. 

 The contiauation of the ribs is preserved only in outline. 



Fig. 6. The unJerside of a part of the pygidium, showinj; the thickened border, the sharp 

 "elevations separating the ribs, and those marking the furrow upon them. The 

 round pits indicate the bases of the large tubular spines, which ornament the 

 surface with some regularity. 



Fig. 7. The lower side of a pygidium, showing the broad thickened border, and the deep 

 cavity made by the protuberance at the extremity of the axis. The bifurcations 

 of the central lobe are more diverging than usual, but this feature is accidental 

 in the specimen. 



Geological position and locality. In the limestones of the Lower Helderberg group : 

 Albany and Schoharie counties. 



Acidiispis tuberculatum. 



Plate LXXIX. Fig. 1 - 14. 



Acidaspii luberculatus : CoXRAD, Annual Report on the Palaeontology of New-York, 1840, p. 205. 



Acaniholoma : Conrad, Ibid. idem. 



AcarUholoma spinosa : Comkad, Ibid. 1841, p. 39. 



Head somewhat semicircular, convex, with the posterior angles greatly 

 extended : length about one-third the entire length of the animal. 



. The frontal border is nearly straight, and bears on its upper margin a 

 row of pustules ; separated from the glabella in the middle of the front 

 by a shallow groove, which becomes much deeper towards the lateral 

 angles. 



Median lobe of the glabella oblong, spreading in front and becoming 

 somewhat semicylindrical behind, giving a subclavate form. The two 

 lateral lobes are small oblong tubercles, separated from each other and 

 from the median lobe by a defined furrow, which is very deeply im- 

 pressed at the anterior inner side of each of the lateral ones. Occipital 

 furrow broad and shallow in the middle, and depressed in a deep pit just 

 behind each of the posterior lateral lobes of the glabella. The occipital 

 annulation is well developed, and, in the centre, produced into a short 

 strong spine, which is slightly ascending and projecting backwards. 



The cheeks ( known only in a separated condition) are triangular ; the 

 inner angle being occupied by the eye tubercle, and the anterior one 



