132 University Geological Survey of Kansas. 



PSEUDOMONOTIS. 



Beyrich, Zeitsch. der Deutsck. Geol. Gesellsch., XIV, (1862). 



Pseudomonotis hawni. Plate XIII, figs. 11-llc; plate XV, figs. 1-lf, 2, 2a. 



Monot/'s haivni Meek and Havden, Trans. Alb. Inst., iv, p. 76, (1858); 



Proc. Acad. Nat. Sci. Phil. 1$59, p. 28. 

 Eumicrotns hawni Meek and Havden, Pal. Upp. Mo., p. 54, pi. n, ff. 



5a-c, (1864); White, 13th Ann. Rep. Ind. St. Geol., p. 142, pi. xxx, 



f. 10, (1884); etc. 



Meek and Hayden's description: "Shell subcircular, or 

 subovate ; hinge straight, equaling about half the length of 

 the valves ; beaks subcentral, short, not oblique ; ears nearly 

 obsolete ; base rounded ; antero-ventral and postero- ventral 

 margins rounded, the latter being somewhat more prominently 

 rounded than the other. Left valve convex ; anterior mar- 

 gin sometimes slightly sinuous near the hinge above ; poste- 

 rior margin intersecting the hinge at an obtuse angle ; beak 

 convex, extending but little beyond the hinge line. Right valve 

 nearly or quite flat ; beak flat, not projecting beyond the hinge ; 

 byssal sinus narrow, deep, or extending back parallel to the hinge 

 to a point nearly under the beak. Surface of both valves, par- 

 ticularly the left one, ornamented by more or less distinct radi- 

 ating costse, which are usually separated by spaces three or four 

 times their own breadth, and armed with regularly disposed 

 vaulted, spinelike prominences, formed apparently from the pro- 

 jecting laminse of growth. Between each two of the principal 

 radiating costse from one to three or four much smaller radiat- 

 ing ribs or lines are usually seen, crossed by obscure concen- 

 tric markings. Hinge and muscular impressions unknown. 

 Length, 1.47 inches ; height, 1.42 inches ; convexity, about 0.40 

 inch." 



Range and distribution : Upper Coal Measures ; Turner, Law- 

 rence, near Topeka. 



To the above synonyms should be added, I think, P. radialis 

 Meek, described in the Nebraska report. From his description 

 and figures, it seems to agree more closely with P. haivni than 

 with any other form. 



