ORTMANN: monograph of the naiades of PENNSYLVANIA. 167 



This species gi-ows somewhat larger in some western streams. 



Soft parts (See Ortmann, 1912, p. 294). Glochidia figured by Lea (Obs. VI, 

 1858, PL 5, fig. 35) (immature), and Ortmann (19116, PI. 89,' fig. 12). 



Breeding-season: Records for gravid females are at hand for: August 7, 1908; 

 Aug. 8, 1908; Aug. 26, 1911; Sept. 13, 1917; Sept. 27, 1909; Oct. 10, 1907; and 

 May, 1908. Glochidia have been found in September, October, and INIay; and 

 on May 14 discharging specimens have been seen. 



Thus this species is bradytictic. The breeding season begins in August and 

 lasts till May. 



Remarks: This is a species, which has a rather indifferent, generally sub- 

 elliptical shape, without any striking features. Externally it looks hke a small 

 Anodonta, and the thickness of the shell is also much like that of Anodonta. More- 

 over the shape of the shell is rather variable, being sometimes longer, or shorter, 

 and more or less compressed. If the beaks are well-preserved, there is no mistake 

 about its identity, since the beak-sculpture is quite peculiar and characteristic. 

 Eroded shells may be distinguished from Anodonta by the hinge-line, which is not 

 so straight. 



In general shape Strophitus edentulus is often much like this species, and, 

 when the beaks are eroded, the two species are sometimes hard to tell apart. But 

 they may be distinguished by the thinner shell of Anodontoides, the interior of 

 which is blueish white and strongly iridescent, while in Strophitus, especially in 

 older specimens, the nacre is more thickened toward the beak-cavity, and there 

 turns pure white, creamy, or even salmon-color, and is not so iridescent. Further 

 in Strophitus the rudiments of the cardinal teeth are more distinct, and the hinge 

 is more incurved in front of the beaks. When the beaks are preserved, Strophitus 

 is distinguished by the heavier beak-sculpture. Of course, the soft parts, chiefly 

 those of the female, when it is gravid, are entirely different in these two species. 



The convexity of the valves varies greatly in Anodontoides fenissacianus, and 

 becomes sometimes rather great, thus approaching the shape of the var. buchanensis 

 (see below). Such specimens turn up now and then among normal ones, and 

 at a few localities more frequently, as for instance, in Conneaut Lake. Some 

 shells from this locality (and also from the outlet of the lake) might safely be called 

 buchanensis; while others, found with them, have the normal, more compressed 

 shape; similar conditions prevail in the uppermost Shenango River, at Linesville. 

 We actually have here the intergrades between the normal form and the variety. 



It should be noted, that the form from Conneaut Creek (tributary to Lake 

 Erie) is the normal form, not the Lake Erie form {buchanensis). 



