NO. 2297. BRACHIOPOD GENUS PLATYSTROPHIA—McEWAN. 411 



at various localities in Kentucky and Tennessee and was found to be 

 present in New York. 



The species is characterized by its small size and subglobose form. 

 The hinge line is always less than the greatest width. The slopes are 

 convex and are covered by nine jfine rounded plications v/hich are 

 separated by furrows of their own width. The fold is low and the 

 sinus shallow. Both the fold and sinus become progressively wider 

 toward the front. 



Near the beak there are three plications in the sinus and four on the 

 fold. Wlien the shell has reached a length of about 6 mm., plications 

 are added by implantation in the sinus and bifurcation on the fold, 

 sometimes between the original plications and sometimes on the 

 slopes. 



This species differs from PlatystropJiia amoena, new species, in its 

 shorter hinge and in that there are, as a rule, more than three 

 plications in the sinus and four on the fold. The latter species shows 

 a tendency toward the loss of plications rather than the addition of 

 them. 



All species of Platystrophia show a tendency to produce mutations 

 which develop many plications on the fold and sinus. This species 

 seems to have developed from one of these mutations. 



Occurrence. — Trenton group: Bigby limestone at Frankfort, Ken- 

 tucky, and vicinity, and Harts ville, Tennessee. Trenton group at 

 EUisburg, New York. 



Coty pes. —Cut. No. 24244, U.S.N.M. 



PLATYSTROPHIA ELEGANTULA TRIPLICATA, new variety. 



Plate 43, fig. 48. 

 Platystrophia lynx Cumings, Amer. Journ. Sci., ser. 4, vol. 15, 1903, p. 41. 



This variety has all the characteristics of the types except that 

 there are only three plications in the sinus and four on the fold. It 

 resembles the shorter hinged mutations of Platystrophia amoena, 

 nev/ species, and may prove to be a variety of that species. 



Occurrence. — Trenton group: Bigby limestone, Duckers and 

 Frankfort, Kentucky; Nashville, Tennessee. Trenton limestone, 

 EUisburg and Trenton Falls, New York, and in Baffin Land. 



Holotype.—C&t. No. 66126, U.S.N.M. 



PLATYSTROPHU ELEGANTULA AMPLISULCATA, new variety. 



Plate 43, fig. 49. 



This represents a variety of Platystrophia elegantula with a decid- 

 edly shorter hinge line than typical specimens and a broader fold and 

 sinus which bear more numerous plications. 



Measurements. — 11.2 mm. along the hinge, 18.5 mm. wide across 

 the middle, 13.5 mm. high, 12.3 mm. thick, 10 mm. sinal width, and 

 6.8 nmi. sinal depth. 



