36 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I48 



Discussion. — The genus is proposed for two species whose most 

 distinctive character is the pit-Hke structure of the glabellar furrows, 

 a feature so far never observed in the Eodiscidae. The type species 

 shows marked affinity with Acidiscus, where the glabellar furrows 

 are relatively short and deep and the occipital furrow has a similar 

 structure. The other described species, Stigmadiscus gibbosus, shows 

 some resemblance to an Agnostid cephalon in the proportions of the 

 various parts. Whether this similarity is purely accidental, or we 

 are dealing with an Eodiscid evolving into an Agnostid, cannot be 

 decided at present, especially in the absence of thorax and pygidium. 



STIGMADISCUS STENOMETOPUS Rasetti, new species 

 Plate 3, figure 5; plate 12, figures 1-7 



Available material. — Several cephala, of which two fairly complete. 



Description. — Cephalon of low convexity. Glabella relatively nar- 

 row, slightly tapered from the occipital ring to the anterior pair of 

 lateral furrows, very slightly expanded in front, somewhat pointed, 

 occupying about two-thirds of cephalic length. Axial furrow deep 

 posteriorly, shallower anteriorly. Longitudinal profile of glabella ris- 

 ing gradually from front to back, where it reaches its highest eleva- 

 tion in the form of a rounded ridge that drops abruptly to the level 

 of the occipital furrow. In some of the specimens there is an indica- 

 tion of a small, broken spine at this highest point, whereas other 

 individuals where the test at this place is well preserved do not show 

 a spine. Occipital ring moderately long (sag.), bearing a short spine. 

 Cheeks slightly convex, downsloping ; lateral border narrow, of even 

 width, defined by a border furrow that becomes progressively shal- 

 lower and broader forward. Posterior border furrow deeper than 

 lateral border furrow, almost straight, slightly convex forward, join- 

 ing the lateral border furrow near the genal angle which is fairly 

 sharp but seemingly not extended into a spine. Posterior cephalic 

 border wider and better defined than lateral border, extended into 

 a short, horizontal spine located somewhat closer to the axial furrow 

 than to the genal angle. The portion of the posterior border beyond 

 the spine is somewhat slanted forward. Surface of test smooth. 

 Length of holotype cephalon 9.0 mm, width 9.9 mm. The largest 

 glabella indicates a cephalon 12.5 mm in length. 



Occurrence. — Collection cs-4. North Chatham. 



Types.— Holotype : U.S.N.M. 146029. Paratypes: U.S.N.M. 

 146030. 



