26 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I48 



LEPTOCHILODISCUS PUNCTULATIS Rasetti, new species 

 Plate 1, figure S ; plate 11, figures 1-7 



Available material. — Four cephala in fair state of preservation. 



Description. — Cephalon of about equal length and width, well 

 rounded anteriorly. Glabella rising steeply above the occipital fur- 

 row, then sloping down toward a low anterior end without much 

 longitudinal convexity, tapered at low, almost uniform rate but for a 

 barely perceptible constriction at one-third the distance from the an- 

 terior end, reaching not far from the anterior border furrow. Occipital 

 furrow deep and wide ; occipital ring at lower level than glabella, 

 extended into a slender, moderately long spine. Axial furrow deep 

 except in its anteriormost portion. Cheeks rising above the axial 

 furrow, convex transversely, in posterior portion sloping down steeply 

 to border furrow. Border defined by narrow but fairly deep border 

 furrow, convex, wire-like, very narrow in frontal portion. A unique, 

 though inconspicuous, feature of the border is a slight widening 

 that occurs at the point where the margin forms an angle of 45° 

 with the sagittal line; here a small pit, distinguishable in all speci- 

 mens, occurs on the upper surface. The portion of the border pos- 

 terior to the pit remains wider than the frontal border. Another 

 characteristic feature of the border is its sinuous outline in frontal 

 view; the border curves slightly downward medially, upward at the 

 sides of the median downbend, then again downward to assume a 

 smooth course laterally. The slight crushing of the test in some 

 specimens has made these features visible in dorsal view also. Pos- 

 terior cephalic border with straight margin from axial furrow almost 

 to genal angle, at this point reaching maximum elevation and sharply 

 turned downward and forward to join the lateral border, possibly 

 extended into a genal spine. Posterior border furrow deep and wide. 

 Surface of cheeks definitely pitted in all specimens ; similar but shal- 

 lower ornamentation on glabella. Length and width of largest cepha- 

 lon 4.4 mm. 



Occurrence. — Collections cs-4 and U.S.G.S. 4216, North Chat- 

 ham. 



Ty/'^.y.— Holotype : U.S.N.M. 146009. Paratypes: U.S.N.M. 

 146010 and 146011. 



LITOMETOPUS Rasetti, new genus 



Description. — Cephalon relatively wide, almost semicircular, with 

 considerable relief. Glabella long and narrow, slightly tapered, 

 reaching the anterior border furrow which therefore merges medially 



