FOSSILS OP THE NIAGAEA GROUP. 153 



CRUSTACEA. 



Genus CALYMENE, Brot>g. 

 Calymene Niagaeensis. 



Plate 6, figs. 14, 15. 



Calymene Niagarensis, Hall ; Geol. Eept. 4th Dist. N. Y., 1843, p. 102, and fig. 3, p. 101. 

 Calymme Blumenbachii, var. Niagarensis, Hall; Pal. N. Y., Vol. II., p. 307, pi. 67, 

 figs. 11 and 12. 



General form elongate obovate, widest at the posterior limit of the 

 cephalic shield, gradually tapering from this point to the anterior bor- 

 der of the pygidium, beyond which it tapers more abruptly. Cephalic 

 shield short and broad, the width twice and a half as great as the length. 

 Glabella very prominent, projecting above the cheeks and eyes ; rounded 

 and full in the center and front ; separated from the fixed cheeks by 

 deep, sharp furrows; the general form conical, rounded truncate ante- 

 riorly, widest across the posterior lobes, which is equal to the length, 

 including the occipital ring, strongly divided by transverse furrows, 

 and showing in the cast, in which condition it is usually found, four 

 pairs of lateral lobes — the two anterior ones narrow and faintly marked, 

 the third small, but rounded and node-like ; the posterior lobes large, 

 having the form of rounded tubercles. Occipital groove narrow and 

 arching forward in the middle. Anterior border of the head narrow, 

 and abruptly curving upward in the middle. Eyes small and promi- 

 nent. Posterior limb of the fixed cheeks broad and extending to the pos- 

 tero-lateral angles of the head. Suture line reaching the anterior border 

 of the head directly in front of the eye, and forming nearly a straight 

 line between these points ; behind the eye it is directed toward the pos- 

 tero-lateral angles of the head with a regular forward curve. 



Thorax consisting of thirteen articulations, the length about twice 

 and a half as long as the entire length of the head, measuring along the 

 axial lobe ; strongly trilobate longitudinally ; the central lobe forming a 

 little more than one-third of the entire breadth, elevated above the lat- 

 eral lobes, and highly arched transversely, separated from the lateral 

 lobes by a sharply marked longitudinal furrow. Lateral lobes flattened 

 on the top for nearly or quite one-third of their width, then more or less 

 abruptly curving downwards to the extremities of the pleura. The ar- 

 ticulations are distinctly arched forward along the center of the axial 

 lobe, and each one is marked in the cast, on each side of the axis, near 

 its junction with the lateral lobes, by a distinct, rounded, more or less 



