20 NEW YORK STATE MUSEUM 



slightly incurving dorsal furrows. Segments transverse and narrow, 12 

 to 14 in number on internal casts, bearing a double median row of 

 strong and sharp tubercles with fine and faint pustules at the side. 

 Pleurae with 12 ribs which are separated by broad, flat grooves; these 

 ribs are narrow, flattened above and divided by a fine median, linear sul- 

 cus. Very small tubercles are scattered irregularly over the ribs. 



These are pygidia quite closely similar to that of Dal. denta- 

 t u s Barrett, of the Port Jervis limestone and the Dal. p 1 e u r o p- 

 t y x Conrad, of the Helderbergian. The differences are these : in 

 Dal. dentatus the ribs of the pleurae are fewer in number, 

 more deeply divided by the sulci and more strongly pustulose ; on the 

 axis the median row of tubercles consists of two, three or four with 

 lesser ones at the sides. In Dal. pleuroptyx the number of 

 axial and pleural segments is generally more than here, the outline of 

 the shield is less sharply triangular and, while the pleural ribs are of 

 much the same character, the ornamentation of the surface is different, 

 consisting of a fine granulation extending over all annulations with but 

 a slight tendency to become coarser on the axis. 



Phacops correlator sp. nov. 



Plate 2, flg. 9 



1892. Phacops (Acaste) cf. anceps Clarke, op. cit. p. 412 



This very interesting fossil I was at one time disposed to regard 

 as identical with Phacops anceps of the Upper Helderberg lime- 

 stone. On comparison with the original specimen, which was described 

 and figured by the writer in volume 9, Archives do museu national do 

 Rio de Janeiro. 1890. p. 16, pi. 1, fig. 3, a difference appears, which 

 will not permit the union of the forms, and this is found in the sharper 

 development of the glabellar furrows. In Ph. anceps, the only 

 known example of which is an internal cast of the cephalon in limestone, 

 there is no trace of the first and second pairs of these furrows, but in 

 Ph. correlator these furrows are quite clearly developed both on 

 internal casts and impressions of the exterior. There is still a degree 

 of uncertainty whether all these specimens may not prove to belong 



