LOWER HELDERBERG ROCKS. 
335 
Fig. 17. The head of a larger individual which shows the transverse furrows, and preserves 
the eyes in their proper form. 
Fig. 18. A larger head, which has few pustules in the space between the eye and the dorsal 
furrow. 
Fig. 19. Frontal view of fig. 17. 
Fig. 20. Profile of the same. 
Fig. 21. View of the lower side of the head of another specimen, showing some crenulations 
along the marginal furrow. 
Fig. 22. The lower side of another specimen in which the granulation is worn from the 
surface of the glabella, and showing the line of the hypostomal suture. 
Fig. 23. The eye enlarged. 
Fig. 24. A portion of the eye, from which the lenses have been removed by weathering. 
Fig. 25. The hypostoma. 
Geological position and locality. In the shaly limestone of the Lower Helderberg 
group : Helderberg moutains, Catskill, Becraft’s mountain, Schoharie, Carlisle, 
Cherry valley, and other places. 
Pliacops lmdsoiiicus (n. s.). 
Plate LXXIII. Fig. 26, 27, 28. 
Head semielliptical, the length greater than half the width ; the posterior 
angles scarcely extended, and slightly rounded. 
Glabella subpentagonal; length nearly one-third greater than the width. 
Frontal lobe very prominent, gibbous above : middle and anterior 
transverse furrows distinctly impressed in the cast; first annular fur¬ 
row faintly defined; first annulation not prominent, with two pustules 
at the summit and a node at each extremity : occipital furrow and 
annulation strongly defined. Cheeks triangular, not produced behind. 
Eyes small, extending backwards to the line of the first annular furrow, 
having an elevation of four ranges of lenses. 
This species is founded on a single head (the test being removed from the gla¬ 
bella), which is more produced in front than the P. logani : the eyes are smaller, 
and not extending so far backwards. 
Fig. 26. The head of this species. 
Fig. 27. Profile of the same. 
Fig. 28. The eye enlarged. 
Geological position and locality. In the compact beds of the shaly limestone : 
Becraft’s mountain, near Hudson. 
