NATURAL SCIENCES OF PHILADELPHIA. 269 



directed as to intersect the neck furrow ; immediately in front of these there 

 are, on each side, traces of another small, very obscurely defined, lateral lobe ; 

 anterior lobe ventricose, and composing much the larger portion of the whole. 

 Neck furrow deep and broad ; its continuation across the posterior side of the 

 cheeks distinct, straight and terminating at the lateral furrows of the cheeks ; 

 neck segment prominent, twice the size of the thoracic segments, and equalling 

 the greatest transverse diameter of the glabella in front, but more depressed. 

 Eyes in the form of somewhat oval, ventricose tubercles, considerably lower 

 than the glabella, from which they are separated by distinct depressions ; 

 placed about half their length in advance of the posterior margin of the cheeks, 

 and without visible facets ; palpebral lobes, depressed, not covering the eyes, 

 but merely connecting with their inner sides, so as to leave the visual area 

 forming an almost isolated tubercle. Cheeks sloping from the eyes into a 

 broad, rather deep marginal sulcus, which is not continued around the front 

 of the glabella, but extends back a little upon the lateral spine; outside of 

 this there is a rather thick, distinctly striated marginal rim, which becomes 

 very nearly obsolete around the front of the glabella. Facial sutures cutting 

 the anterior margin nearly on a line with the eyes, but curving so as to leave 

 a small semicircular wing on each anterior lateral margin of the glabella; in- 

 tersecting the posterior margin of the cheeks about midway between the late- 

 ral angles and the neck segment. 



Thorax nearly as long as the glabella, exclusive of the neck segment ; dis- 

 tinctly trilobate ; axal lobe slightly wider than the lateral lobes, rounded and 

 rather prominent ; its nine segments narrow and straight, or not arching for- 

 ward. Lateral lobes more depressed, somewhat flattened on the inner and 

 rounding down to the lateral margins ; segment" duplicated by a nearly me- 

 sial furrow extending from their inner ends out to, or a little beyond the 

 undefined knee, beyond which they are obliquely flattened for folding to- 

 gether and rounding at their extremities. 



Pygidium a little more than oue-fourth wider than long, rather distinctly 

 convex, rounded behind and more or less straight in front, with anterior late- 

 ral angles obliquely truncated and a little rounded. Mesial lobe very promi- 

 nent and well defined, rounded above, and a little flattened or furrowed on the 

 sides ; as wide anteriorly as the lateral lobes, tapering and declining some- 

 what posteriorly to an abrupt, obtuse termination, about half its own greatest 

 anterior breadth within the flattened margin ; segments, fourteen or fifteen, 

 distinctly defined, smaller than those of the thorax. Lateral lobes depressed 

 below the mesial lobe, somewhat flattened on the inner side, and sloping to the 

 rather narrow and more flattened border; segments ten, somewhat oblique, 

 well defined for three fourths of the distance out, and thence less distinctly 

 so, to within a short distance of the margin ; a few of the anterior ones with 

 an obscure longitudinal furrow. 



Surface granulose, the granules being largest on the posterior portions of 

 the glabella, palpebral lobes and neck segment. On the segments of the axal 

 lobe, both of the thorax and pygidium, as well as on those of the lateral 

 lobes, they are very small and regularly disposed, so as to form a single row 

 to each segment. 



Entire length, 1-19 inches; about, 0'70 inch. Length of pygidium, 0-44 

 inch; breadth of do. , 0-5t> inch. Length of thorax, 0*33 inch; breadth of 

 do. 0.60 inch. Length of cephalic shield, 0-42 inch ; breadth of do. - 64 inch. 

 Length of glabella, exclusive of neck segment, 0-36 inch ; breadth of do. 

 0*24 inch. Length of eyes, 0-13 inch. 



This species is remarkable for the structure of its eyes, which, instead of 

 being, as usual, cuvered by the palpebral lobes, have the form and appear- 

 ance of distinct oval tubercles, with the palpebral lobes very small, depressed 

 to, or a little below the elevation of the eyes, and merely connecting with 

 their inner side. We have not been able to see any facets in the eyes, even 

 under a good lens, but they doubtless existed beneath the external crust. 



1865.] 18 



