68 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 148 



from Missouri, including the pygidium. The assignment of the two 

 parts of the shield is confirmed by the specimens illustrated herein. 



Occurrence. — The type locality is U.S.N.M. 22t in the Thorn Hill 

 section, in the interval 45-133 feet above the base of the formation. 

 Also in author's collection cnd/10, Comby Ridge. 



Types. — Holotype and paratypes: U.S.N.M. 94883. Plesiotypes: 

 U.S.N.M. 144619. 



Genus HOLCACEPHALUS Resser, 1939 



Type species. — Holcacephalus granulatus Resser. 



HOLCACEPHALUS GRANULATUS Resser 



Plate 3, figures 12-14 



Holcacephalus granulatus Resser, 1938a, p. 81, pi. 9, figs. 15-17. 



Available material. — The species, quite common at the type locality, 

 was not found elsewhere. All the available specimens lack the test. 



Description. — Glabella definitely tapered, defined by a deep axial 

 furrow, with two pairs of short, but deep lateral furrows, and another 

 pair less distinct. Occipital furrow deep, occipital ring long (sag.), 

 bearing a short, very slender spine. Preglabellar field downsloping, 

 border narrow, well defined by the border furrow. Ocular ridges trans- 

 verse ; palpebral lobes at level of anterior third of glabella ; palpebral 

 area almost as wide as anterior portion of glabella. Posterior area 

 slender, slightly expanded distally, bearing a genal spine that is broken 

 off in almost all available specimens. Surface covered with relatively 

 large granules. 



Pygidium twice as wide as long, subelliptical ; with posterior outline 

 slightly indented medially. Axis occupying almost entire length, with 

 4 prominent rings. Pleural lobes slightly convex, lacking border furrow 

 or border. Three pairs of pleurae are clearly separated by interpleural 

 grooves ; each pleura is furrowed and the posterior band bears a row 

 of tubercles like those on the cranidium. 



Discussion. — This species differs considerably from all others hith- 

 erto attributed to the genus in the tapered, deeply furrowed glabella. 



Occurrence. — Red limestone beds at the base of the Nolichucky 

 (Cedaria zone) at U.S.N.M. locality 27d (= author's locality cnd/1), 



Ty/^^.?.—Cotypes: U.S.N.M. 94844. Plesiotypes: U.S.N.M. 144620. 



HOLCACEPHALUS PRAECURSOR Rasetti, new species 



Plate 3, fig-ures 10, 11 



Available material. — Several cranidia and pygidia. 



Description. — Owing to the similarity to the preceding species, it is 

 sufficient to point out the differences. The anterior border is somewhat 

 wider and flat instead of convex ; the ocular ridges are more prominent ; 



