CONTRIBUTIONS TO PALAEONTOLOGY. 109 



cylindric axis marked by nine annulations : lateral lobes nearly 

 flat for half their width; the ribs sharply grooved; the anterior 

 limb angular on the margin. 

 The pygidium is remarkably elongate, having a length and width 

 almost precisely equal : the axis prominent; section semiellipti- 

 cal, the height being more than half the width, and very gra- 

 dually tapering to an obtuse point; marked by twenty-two an- 

 nulations which are vertical on the sides, but a little bent forwards 

 on the summit of the axis. Lateral lobes flat near the axis, thence 

 curving gently to near the middle of the width, and bending 

 more abruptly downwards; marked by twelve ribs, and termina- 

 ting in a broad sloping border which is abruptly turned upwards 

 at the margin. Surface finely granulose. 



This species is remarkable in having but nine articulations of the thorax, 

 in the extreme elongation of the pygidium, and the number of rings in the 

 axis. The glabella is more prominent between the eyes, than in any species 

 which I have seen. In all these respects, and in the absence of nodes at the 

 base of the occipital ring, it diifers so greatly as to afford few points of 

 similarity with any of the species described in this paper. 



Geological formation and locality. This species, together with a Pha- 

 COPS undistinguishable from P. hufo^ var. rana, were given to me by Rev. 

 Mr. Nash of Desmoines, Iowa ; who informed me that they were from some 

 point far to the northeast of that place, the particular locality having been 

 lost or forgotten. The region indicated is occupied by a broad belt of the 

 Hamilton group, and I presume this speeies to be from rocks of that age. 



GENUS LTCHAS (Dalman). 



LICHAS Aaj VHrT ffl ( n.s.). "i^^^^ ^ H '^ 

 In the collections from Western New -York, there are several 

 fragments of a species of Lichas, in many respects similar to L. 

 piistulosusj and also to L. bigsbyi. The pygidium is rounded to the 

 limits of the border on the lower side, making very nearly a semi- 

 circle, the centre being at the anterior margin of the axis. The axis 

 is marked by three indistinct rings on the upper half; and in the 

 middle it becomes very gibbous and surmounted by a strong spine, 

 the other portions of the surface nodose. The lateral lobes are deeply 

 grooved; the anterior limb marked by small nodes, and the posterior 

 limb by a row of strong elevated nodes with intermediate smaller 



1861.] 7^ iiAwtdJ^s i^^*-^ Vo^iX^az f <xr J "c. ^ •' I 



