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PALEONTOLOGY OF NEW-YORK. 



Buckler semicircular or sublunate ; glabella marked by three tubercles on either side, the 

 lower of which is much more prominent, and the upper one scarcely distinct ; body gradually 

 tapering from the base of the head, composed of thirteen articulations, those of the middle 

 lobe being bent abruptly upwards at their extremities, which are prominent ; articulations of 

 the lateral lobes compressed towards their extremities, and rounded, a distinct longitudinal 

 groove reaching nearly their whole length, but usually visible only about half their length, or 

 to the arching of the ribs ; caudal shield with about eight articulations in the middle lobe 

 and five in each lateral lobe, those of the lateral lobe grooved nearly to the margin, which is 

 thickened and reflexed ; entire surface granulated. 



There has been much difficulty in identifying our specimens positively with the European 

 species known under this name. A comparison with a Dudley specimen shows some slight 

 differences, but perhaps not sufficient for a separation of species. Our specimens are always 

 smaller ; the second or smaller lobe of the glabella is less conspicuous, being in fact often 

 scarcely visible, while the front is slightly narrower ; the articulations of the middle lobe of 

 the body are less prominent and rouoded at their terminations, and never nodulose. Beyond 

 these and other similar minor differences, the two correspond. 



Between the Niagara and Trenton specimens, I am able to perceive really but slight 

 differences ; and a comparison with specimens from Gothland shows that there is too little 

 difference for the satisfactory establishment of distinct species. We must therefore regard the 

 Calymene blumenbachii as appearing in the Trenton limestone and the intervening rocks to the 

 termination of the Niagara period. In the lower Helderberg limestones, which are prolific in 

 fossil trilobites, there is no representative of this species ; but in the Schoharie grit there is a 

 large species having similar characters, but differing too widely to be referred to the same. 



In the shale of the Niagara group this species is extremely abundant, often occuring in groups 

 upon the surfaces of slabs of the shale. It is rarely found in the limestone of this group in New- 

 York ; though at Springfield, Ohio, it occurs in limestone of the same age. 



Fig. 11. An entire individual of the largest size, found in the shale of the Niagara group. 

 Fig. 12. A fragment of shale having upon its surface three entire specimens of this species. At 



a there is the caudal shield of a Homalonotus, and at b the caudal shield of Pkacaps 



limulurus. 



Position and locality. In the shale of the Niagara group at Lockport, Rochester and other 

 places ; also in the limestone at Lockport. 



