9S9 pala:oxtology of new-youk. 



head, and another one preserving the head and part of tlie thorax and several 

 articulations of tlie pjgidiuni, and a separate pygidluni; but tlie whole are so muti- 

 lated as to afford very unsatisfactory evidence of tlie entire character of the species. 



Fig. 5. Tlie head of this species. 



Fig. 6. A fragment preserving the head and part of the thorax. 



Fig. 6 a. Lateral view of the same. 



Fig. 7. The pygidium of another individual. 



Fig. 8. An enlargement, showing the surface marking. 



Geological position and locality. In the pentamerus limestone of the Lower Hel- 

 derberg group : Schoharie county. 



IIoiualiHiotus vaiiuxeiiii ( n. s.). 



Plate LXXIIL Fig. 9 - 14. 

 Head unknown. 



Thorax long : sides subparallel, the middle lobe flattened on the exterior 

 surface ; articulations arching forward ; longitudinal furrows faintly 

 defined, being a simple undulation in the articulations ; lateral lobes 

 narrow, the articulations bent abruptly downwards at the sides. 



Pygidium subtriangular with the articulating side much longer and broadly 

 curving, extremely convex : axis prominent in the young specimens, 

 and becoming subdued in older ones; width, at its upper extrernity, 

 equal to that of each of the lateral lobes. Annulations fourteen or fif- 

 teen in the cast, and twelve ribs visible on each of the lateral lobes. 



Surface of the test punctate and striato-punctate : cast punctate. 



This species is known from tlu-ee specimens of the pygidium ( two of which are 

 imperfect at the posterior extremity), and a fragment of the thorax; no specimens 

 of the head having come under my observation. The thorax differs from the Niagara 

 species in the forward arching of the articulations of the axis, while those of the 

 lateral lobes are thicker towards their extremities. 



The pygidium of this species differs from that of H. delpkinocephalus in the lesser 

 prfiminence of the base of the axis and its greater number of articulations, which 

 are more distinct, and the lower margin of each one more abrupt; and while we 

 have in the lateral lobes of the Niagara species six or seven, and rarely eight or 

 nine ribs, there are in this species twelve, counting in both instances the upper one, 

 which is usually covered by the last thoracic articulation. 



