TRILOBITES. alia 
Gerasaphes ulrichana | 
outward curve following the margins of the frontal glabellar lobe, and recurving 
anteriorly, the branches of the suture meeting at an angle in the median line at, or 
just within the frontal margin of the cephalon. Between the anterior limbs of the 
suture and the frontal lobe is a smooth, flat area. 
The glabella is broad and expanded anteriorly, narrowing backwards, its 
anterior width being fully twice that at the occipital ring. Its surface is quite 
smooth and evenly convex with an obscure median longitudinal ridge traversing its 
entire length. The extreme Jateral points of the frontal lobe lie about one-fourth 
the length of the glabella from the anterior margin; thence the lateral outlines 
converge in nearly straight lines to points just above the palpebral lobes, where 
there is a slight inward deflection on each side, which represents the position of the 
first glabellar furrows. Below this is a pair of more conspicuous depressions, or the 
second lateral furrows, which begin opposite the middle of the palpebral lobes, pass 
directly inward for a short distance and then backward, extending quite to the 
occipital furrow. These furrows are not deep but the lobes thus cut off are quite 
distinct. The posterior median portion of the glabella between these furrows is 
narrow and the low axial ridge traversing it terminates at the neck ring in a round, 
blunt elevation. These features, with the exception of the prominence of the basal 
lobes, are throughout characteristic of the typical Asaphus, and the accompanying 
figure may be compared with that of Asaphus expansus given on a preceding page. 
The occipital ring is arched and moderately prominent. 
Figs. 15, 16.—Pygidia of Gerasaphes ulrichana, x 5. 
Pygidium multisegmented, outline subparabolic, margin entire. Surface very 
convex medially, lateral portions depressed convex. Border broad and flat, being 
widest at the post-lateral edges, narrowest at the anterior angles and posterior 
extremity. At the latter point there is a slight incurvature of the margin. The 
outline of the convex portion of the shield is subtriangular and quite different from 
that of the margin. 
Axis quite narrow, highly convex, longitudinally arched and extending to the 
marginal border. It bears 10—11 distinct annulations, the anterior ones being 
separated by broad grooves. Only the posterior extremity is unsegmented. 
The pleurz bear 7 ribs on each side; these are narrow, straight, transverse, very 
slightly reflected except at their outer extremities on the margin. Kach of these 
sharply defined ribs is divided by a deep sulcus, broader than the interannular 
