626 



MEMOinS OF THE CARNEGIE MUSEUM. 



fact that Von Iheriiig did not measure in the way I did (See p. 526). If I measure 

 the length of my specimens along the longest axis (diagonally), and the height 

 vertically to it, I obtain for the above specimens figures more nearly agreeing with 

 those of Von Ihering from 51 to 59 pr. ct. of length. 



Measuhements. 



In other respects, the characters given b}^ Yon Ihering for riograndensis agree 

 with my specimens. This is especially true of the diameter, which, according 

 to Von Ihering ranges from 30 to 39 pr. ct., and in my specimens from 34 to 40 pr. ct. 

 Von Ihering believes that the diameter as well as the height differ according to 

 sex. According to my material there surely is no such differentiation. It is im- 

 possible to directly compare my measurements for the location of the beaks (29 

 to 33 pr. ct.) with those given by Von Ihering, because he measured the distance 

 from the anterior end of the hinge-line (34 to 43 pr. ct.); but I should say that 

 measurements of my specimens taken in the same way give, for the above speci- 

 mens, the values: 36, 35, 37, 43, 40, 44 pr. ct. of length, agreeing fully with \^on 

 Ihering's. 



The point of the beaks is inclined forwards, as Von Ihering mentions, but 

 not too much stress should be laid upon this character. An im]iortant feature, 

 however, is the curved hinge-line. 



Glabaris trapesialis cygneiformis Pilsbry (1S96, p. 563, PL 26, figs. 4, 5) from 

 Maldonado, Uruguay, surely is closely allied. But, as Pilsbry points out, it is 

 more compressed than riograndensis (Diam. only 26 pr. ct.), and its posterior end 

 is more elevated above the base-line; it is thus less oblique. For this reason I 

 cannot unite it with the present species, although it may fall under it. 



Glabaris simpsonianus Pilsbry (ibid., p. 564, PI. 27, fig. 13) from Rio de la 

 Plata, is also very much like riograndensis. The height of 56 pr. ct. and the diam- 

 eter of 38 pr. ct. fall within the range of variation of riograndensis. But it is said 

 to be a very solid shell, of a rather regular, oblong-oval shajjc, with a large, elongated 

 anterior protractor scar. Having no specimens corresponding to it, I cannot express 

 an opinion. 



Anatomy. — The soft parts of three males and two gravid females are at hand, 



