DESCRIPTION OF GENERA AND SPECIES. 221 
Genus ASAPHISCUS Meek. 
Asaphiscus MEEK, 1873. (See Walcott, 1886, Bull. U.S. Geol. Survey, No. 30, p. 219.) 
Asaphiscus iddingsi Walcott. 
Plate 23, Figures 1, 1a—b. 
Asaphiscus iddingsi WaLcort, 1911, Smithsonian Misc. Coll., vol. 57, No. 4, pp. 99-101, plate 16, 
fig. 3. (Described and discussed as a new species essentially as below.) 
Dorsal shield longitudinally oval in outline, moderately convex. Cephalon 
semicircular in outline; a little more than one-third of the entire length of the dorsal 
shield; bordered by a nearly flat or slightly rounded margin that passes at the genal 
angle into a moderately strong genal spine; within the genal spine a rounded 
posterior border is separated from the fixed cheek by a rounded, clearly defined 
furrow; the intermarginal furrow is shallow and rounded. Cranidium moderately 
convex and roughly subquadrate in outline; the frontal limb is slightly convex and, 
with the anterior portion of the glabella and the front margin, forms a gentle slope 
that is broken only by the slight dorsal furrow in front of the glabella and the 
shallow intermarginal furrow; the frontal limb merges on the sides into the fixed 
cheeks, which are a little less than one-half the width of the glabella; posteriorly 
the fixed cheeks merge into relatively small postero-lateral limbs; palpebral lobe 
narrow and extended in front as a low ridge that crosses the fixed cheek to the 
dorsal furrow near the antero-lateral angle of the glabella; that portion of the 
palpebral lobe above the eye is about one-fourth the length of the cephalon. 
Glabella large, slightly narrower in front than at the occipital furrow; sides 
nearly straight and slightly converging, frontal margin broadly rounded; surface 
marked by very faint impressions of three pairs of glabellar furrows, which can only 
be seen where the surface is very perfectly preserved. Occipital ring about as wide 
as the frontal margin and separated from the glabella by a shallow furrow that 
terminates on the side slightly in advance of the posterior intermarginal furrow. 
Free cheeks about as wide opposite the eye as the fixed cheeks; eye-lobe about 
one-fourth the length of the cephalon. Postero-lateral angle continued backward 
into a moderately strong spine. The facial sutures cut the posterior margin just 
within the genal angle and extend obliquely inward with a slightly sigmoid curvature 
to the base of the eye-lobes; curving over and around the eye-lobes, they pass 
forward and a little outward, cutting the frontal margin obliquely. 
Thorax with nine segments; axial lobe moderately convex, slightly narrower 
than the pleural lobes in compressed specimens; on the outer side of each segment 
a low, rounded node or ridge is separated from the main body of the segment by a 
slightly oblique furrow transverse to the segment; pleural lobes slightly convex, 
nearly flat out to the geniculation, where they curve slightly downward and back- 
ward; each pleura has a well-defined furrow starting near the inner anterior margin 
and extending backward to the center of the pleura at the geniculation, where it 
curves slightly backward and terminates on the broadly rounded, slightly falcate 
end of the pleura. 
Pygidium roughly semicircular in outline, one-fourth the length of the dorsal 
shield; anterior margin nearly transverse at the axial lobe and curving slightly 
backward to conform to the curvature of the last thoracic segment; axial lobe 
moderately convex and tapering gradually toward its posterior section, which is just 
within the nearly flat marginal border; it is divided by four transverse furrows into 
four rings and a terminal section; three anchylosed pleural segments are outlined 
on the pleural lobes by furrows that curve backward and terminate on the inner 
margin of the doublure; this line is continued forward on the pleural lobes of the 
thorax, terminating on each side opposite the posterior end of the facial suture. 
