244 PAUEONTOLOOT OF NEW>TOBK. 



Fig. 1 g. The cephalic shield, represented in fig. 1 a ; showing the separation of the maxillte y y at the 

 facial sutures. 



Fig. 1 k. The right raaxilla, separated from the cephalic shield, as it appears in a fragment of the lime- 

 stone. 



Much confusion in regard to this species exists in the works of foreign authors, several 

 distinct forms being erroneously referred to the same ; while the real one, which doubtless 

 occurs in several localities, is referred to another genus. Capt. Poetlock, though disposed 

 to recognize and identify all American species, has failed in this instance, and his Amphion 

 gelatinosus can scarcely be any other than our species. This difficulty has arisen in part 

 from the obscure specimen from which Geeen's cast was made, the character of the buckler 

 being very indistinct, though the nodulose articulations are well preserved. 



EitHEiCH, in his memoir, remarks that the Amphion gelatinosus of Poetlock belongs to 

 Phacops, a section of the Genus Calymene of Beongniaet, having reticulated eyes. This is 

 quite untrue, however ; for the eyes of Ceraurus are peculiar, and quite different from 

 those of Phacops, as they are from those of Calymene ; while the facial suture is similar in 

 direction to the former, and the labrum, as in that genus, is attached by a suture to the 

 front of the glabella. 



More recently, Dr. Loven {id cit.) has attempted to prove the identity of Ceraurus, 

 Odontopleura and Addaspis ; but he has misapprehended the characters of the Ceraurus, 

 owing to the obscurity of the model of Green. I shall hereafter be able to show that the 

 Ceraurus is restricted to the lower epoch of our pala;ozoic strata, while Acidaspis {Odonto- 

 pleura) is a genus continued into the lower and middle palaeozoic strata, and differing 

 essentially from Ceraurus in many other particulars, as well as in the direction of the 

 facial suture. 



I have given the numerous figures of this species, and of the parta usually found in the 

 Trenton limestone, with a view of establishing the characters of the genus, and its clear 

 distinction from other genera of Trilobites in the older strata. Notwitlistanding all that is 

 given, however, the entire characters of the species are not represented, as will be seen 

 from the transverse view of a single articulation ( Pi. 65, fig. In), which is well preserved 

 on the surface of a slab of limestone, showing the extended extremities, which bend 

 abruptly downwards and curve slightly backwards, terminating in an obtuse point. 



Position and locality. This species, so far as known in New-York, is restricted to the 

 period of the Trenton limestone. It is found at Middleville, Trenton falls, Lowville and 

 Watertown, and is more rarely seen in localities in the Champlain valley. It is also known 

 in several western localities and in Canada, showing a wide geographical range. The large 

 fragment figured on Plate 66 is from near Cincinnati, Ohio. 



