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PALEONTOLOGY OF NEW-YORK. 



nearly the same width as the front, and reaching to the base of the eye-tubercles ; lateral lobes 

 of the glabella oval-ovoid, having their longitudinal axis directed obliquely forward ; oruliform 

 tubercles auriform, broader at the base ; transverse furrow broad and well defined, extending 

 nearly to the posterior angles of the buckler ; facial suture coming to the base of the buckler 

 about half way between the base of the eye and the posterior angle ; thorax composed of 

 eleven articulations ; axis convex, gradually tapering to the posterior extremity ; lateral lobes 

 with the articulations flat, falcate, a distinct broad groove extending the entire length, and 

 terminating in the acute extremity. Pygidium laciniate ; axis marked by two narrow articu- 

 lations above, and a third posterior one which is prominent and very convex in the middle, 

 from whence it abruptly slopes downward, becoming conllucnt with the expanded border ; 

 lateral lobes composed of three articulations which are much expanded in the middle, but 

 contract to acute points below, forming the laciniate margin. Entire surface scabrous, having 

 the acute pustulose points directed backwards. 



The under side of the crust shows puncta corresponding to the pustulose elevations on the 

 upper side, and the same striated or lamellose surface towards the extremities. The clypeus is 

 attached directly below the front of the glabella : it is broadly rounded in front, and obtusely 

 bifurcate behind. A little behind the centre it is depressed in the middle ; and on each side, 

 equidistant from the margin and each other, are two strongly marked depressions, from which 

 proceed grooves extending obliquely forwards, and curving round the anterior portion of the 

 clypeus. A little outside and behind these depressions are two others, less deep, and com- 

 municating with the groove just mentioned by a more shallow one. Margin of the clypeus 

 striated ; central portion with oblong or angular punctures. 



This species, in an entire condition, is one of the rarest as well as most beautiful trilobltes of 

 the group, though fragments of the buckler and pygidium are not unfrequently found in the shale. 

 It is easily recognized, however, from any other species, by the peculiar surface marking : the 

 form and terminations of the articulations either of the body or tall, and the glabella and other 

 portions of the head arc equally characteristic. The form alone, of the eyes, is all that can be 

 determined j since in all the specimens seen, they are more or less crushed, and the upper 

 margin projects beyond the base so that the lateral or vertical portion is broken off, or left 

 attached to the matrix. In the larger number of specimens the eye-tubercle is so mutilated that 

 it is scarcely to be recognized as that organ, and is not always distinguished from the lobes of 

 the glabella. The projecting portion anterior to the prominent front of the glabella, appears 

 rather to be an expansion of the margin or border which surrounds the front of the buckler j 

 and at its edge, and beneath, Is striated or lamellose. A partial exfoliation of the crust from 

 the upper surface shows beneath it the same striated surface, which, at the base, extends in- 

 ward nearly as far as the point where the facial suture comes out, and gradually narrows above, 

 till at the lateral anterior margins of the glabella it has scarcely a perceptible width ; but from 

 this point it again expands, forming the projection in front. The outer extremities of the 

 articulations, for more than one-third of their length in the upper part of the body, and one half 

 their length in the lower part, are striated, or sharply grooved across in lines continuous with 



