NO. 2297. BRACHIOPOD GENUS PLATYSTROPHIA—McEWAN. 417 



Measurements. — 12 mm. along the hinge line, 14.5 mm. across the 

 middle, 9.6 mm, high, 7 mm. tliick, 5.4 mm. sinal width, 4.7 mm. 

 sinal depth, 2 mm. fold depth. 



Occurrence. — Maysville gi-oup. Near the base of the Fairmount 

 beds; Newport and Covington, Kentucky. 



Cotypes.— Cat. No. 65946, U.S.N.M. 



PLATYSTROPHIA PAUCIPLICATA Cumings. 



Plate 47, figs. 13-15. 



PUitystrophia lynx pauciplicatu Cumings, Amer. .Tourn. Sci., ser. 4, vol. 15, 1908, 

 p. 23, figs. Obis. 



Professor Cumings has described this small pauciplicate form from 

 the Maysville of Cincinnati, Ohio. It varies from thin to strongly 

 convex. The low, slight!}' compressed fold has four plications which 

 result from the bifurcation of two primary plications at the beak. 

 The shallow sinus has one median primary plication and two second- 

 ary plications which are situated on the opposite slopes of the sinus. 



The hinge line is generally less than the width across the middle. 

 The cardinal areas narrow rapidly. There are five and six plications 

 on the lateral slopes of which the outer ones curve as they approach 

 the lateral margins. 



This species differs from Platystrophia juvenis, new species, in that 

 it has fewer and more widely spaced plications, in the curvature of 

 the plications next to the cardinal angles, and in posessing a slightly 

 compressed fold. 



So many characteristics in common between the two species sug- 

 gest close relationship, and it is likely tliat Platystrophia juvenis was 

 the direct ancestor of Platystrophia pauciplicata if the many interme- 

 diate forms are taken as evidence. Transitional forms suggest that 

 Platystrophia pauciplicata gave rise to Platystrophia crassa by increase 

 in gibbossity and decrease in relative index.' 



Measurements. — 14 mm. along the hinge line, 14.9 mm. wide across 

 the middle, 10 mm. high, 8.3 mm. thick, 7.3 mm. sinal width, 5 mm . 

 sinal depth, 2 mm. fold depth. 



OccwrreTice.— Maysville group: Base of the Fairmount beds, Cor- 

 ington, Kentucky, and Cincinnati, Ohio. 



Plesiotypes.— Cat. No. 65947, U.S.N.M. 



PLATYSTROPHIA STRIGOSA, new species. 



Plate 43, figs. 23-26. 



Tills name is used to designate specimens with thin valves and low 

 spreading folds and shallow smuses on which the lateral plications 

 are dwarfed. The hinge-line equals or is somewhat greater than the 



1 Relative index is the length of the hinge line divided by the height. 

 115690— 19— Proc.N.M.vol.56 27 



