OETMANN: monograph of the naiades of PENNSYLVANIA. 197 



not ovate (higher anteriorljO- Then again the ovate outUne, with the anterior 

 part of the shell high, and the posterior part more or less tapering, is also repre- 

 sented in typical S. edentulus with compressed shell. 



The real S. undulatus therefore remains a disputed form. 



Of course S. undulatus, as discussed here, is not fully identical with Simpson's 

 undidatus, for Simpson included in this all small, thin, and generally distinctly 

 biangulate sheUs (Simpson, 1900, p. 618, footnote). But these characters well fit 

 young specimens of S. edentulus, while the specimens received from Conner are not 

 biangulate behind, on account of the tapering posterior end. 



Locality represented in the Carnegie Museum: 



Delaware River, Newbold, Gloucester Co., New Jersey (C. H. Conner). 



Distribution (See fig. 21): Frierson has sent me for examination a specimen 

 from Warwick Pond, Warwick, Rhode Island, and another one from Orange Co., 

 Virginia, but I have not been able to satisfy myself that they belong here, as was 

 supposed, and that they are a species distinct from S. edentulus. Johnson (1915) 

 keeps S. undulatus apart from S. edentulus, and gives for the former, a nmnber of 

 localities in New England, but I have no means of deciding what he understood 

 by this species. No other records are knowTi positively referring to this form. 



Strophitus EDENTULUS (Say) (1829). 

 Strophitus edentulus (Say) Simpson, 1914, p. 345, and Strophitus undulatus Simpson 

 (pro parte), ibid., p. 349. 



Plate XII, figs. 7, 8. 

 Records from Pennsylvania: 



? Lea, Obs. X, 1S63, p. 450 (Schuylkill River, PhUadelpliia)."^ 



Bruckhart, 1869 (as edentula) (Lancaster Co.) 



Hartman & Michener, 1874 (as edentula) (Brandywine Creek, Chester Co.) 



Harn, 1891 (as undulata) (western Pennsylvania). 



Schick, 1895 (as undulata) (Canal, 27th ward, PhUadelphia). 



Marshall, 1895 (as edentula) (Allegheny River, Warren Co.) 



Rhoads, 1899 (as edentula) (Ohio River, Coraopolis, Allegheny Co., and Beaver, Beaver Co.; Beaver 



River, Wampum, Lawrence Co.) 

 Ortmaun, 19096 (as undulatus), p. 194, 202, 207. 



Characters of the shell: Shell of medium size, rather thin when young, moder- 

 ately thick when old. Outline subeUiptical to subovate, broadly rounded in front, 

 more narrowly rounded behind, sometimes somewhat pointed or biang\ilate behind. 



"^ Lea frequently refers to A. undulata as coming from the Schuylkill River. He distinguishes it 

 from A . edentula, but we cannot tell which form he had in mind. 



