60 Field Museum of Natural History — Geology, Vol. IV. 



est elevation just in front of the center, to which point it rises gradually 

 from the posteror and lateral margins and much more abruptly ante- 

 riorly; subpentangular in outline, widest in front of the eyes; a single 

 pair of glabella furrows originates on the lateral margins, curves abruptly 

 inward and upward, then converges backward until it meets the occipital 

 furrow, forming a large median lobe and two smaller lateral lobes. 

 Median lobe very broad anteriorly, more than twice the width at the 

 occipital furrow. It comprises nearly two-thirds of the glabella. 

 Lateral lobes undivided, margins subparallel, conforming to the general 

 convexity of the glabella, abruptly bent downward anteriorly. Occipital 

 segment a flat or slightly concave, transverse band, widest at the 

 juncture of the occipital and glabella furrows, narrowing slightly to the 

 median line and' more so laterally. Occipital and glabella furrows nar- 

 row but distinct. Surface smooth to the naked eye, but a magnifier 

 shows it to be covered with variously sized pustules. No nodes or spines 

 interrupt the regular curvature of the cephalon. 



Thorax and pygidium unknown. 



The specimen here described (Mus. No. P 11257) consists of an 

 incomplete glabella. The cheeks and marginal border are entirely 

 missing. The median lobe and one lateral lobe are nearly complete, and 

 the other lateral lobe is somewhat less so. The occipital, one dorsal and 

 the glabella furrows are well indicated and the median portion of the 

 occipital segment is intact. While the specimen leaves much to be 

 desired, yet the generic characters are well shown and the specific char- 

 acters fairly well. 



The dimensions are as follows: 



Length of glabella on median line (exclusive of occipital 



segment) 24.5 mm. 



Greatest width of glabella (in front of the eyes) 30 mm. 



Width of glabella at occipital furrow 26 mm. 



Width of median glabella lobe on anterior margin, about . . 24 mm. 



Width of median glabella lobe on occipital furrow 11 5 mm. 



Width of lateral glabella lobes 8.5 mm. 



Length of lateral glabella lobes 17 mm. 



Width of occipital segment on median line 3.5 mm. 



Width of occipital segment behind glabella furrows 4.2 mm. 



Amphilichas clermontensis is distinguished from the other members of 

 this genus by the much greater width of the glabella in proportion to its 

 length and by its more nearly arcuate curvature both longitudinally and 

 transversely. In surface ornamentation it resembles A. circullus from 

 the Trenton, but in form it is quite distinct from that species. 



Locality and horizon. — Lower Maquoketa beds, Clermont, Iowa. 



