NAIADES OF MISSOURI 7 1 



except perhaps shorter laterals arranged at right angles to the 



interdentum. 



Sex Length Height Diameter Locality 



c?" 57 X 57 X 40 mm (Miss. R., LaGrange) 



9 56 X 56 X 34 " ( " " " ) 



cf 46 X 46 X 30 " ( " " " ) 



9 23 X 21 X 10.5 " (White " Hollister) 



The latter measurement is of a juveniles from a lot identified 

 by Mr. Frierson as approaching granijera although would perhaps 

 fall more under tuber culata. However, it meets the test of granifera 

 in length and height being about equal and in prominent beaks. 

 Its beak sculpture consists of numerous, fine concentric corrugations 

 extending out on disk somewhat like Q. quadrula. In general 

 shape of shell and dispositition of tubercules it is also like the 

 latter in this adolescent stage. 



Miscellaneous Remarks: — According to shell measurement, 

 and with an allowance for eroded beaks, the Osage forms may be 

 more classed under granijera. A divergence of equality for length 

 and altitude may indicate and approach to the tuberculata, Lea's 

 type, when diameter may be reduced to unity, it measures length 

 and height the same. On this same basis so many of the Rotun- 

 dariae of South Missouri would approach more nearly to the 

 granijera type. Because of its full, projecting beaks, uprightness 

 of shell and disk sculpture this species has sometimes been 

 confused with Q. pustulosa and P. cooperianus. However, dis- 

 tinction can be easily made by comparing to the rich purple nacre 

 of granijera — a color that is not possessed by either pustulosa or 

 cooperianus. Its breeding season is found to be the same as that 

 of tuberculata. Despite their identity of breeding habits, of repro- 

 ductive and nutritive structures and of internal shell characters 

 there may be sufficient evidence of difference in external shell 

 structures to make granijera a good species and thus take it out 

 of its class as a subspecies of tuberculata, as Simpson had treated 

 it, and elevate it as Mr. Walker considers. 



Genus Plethobasus Simpson. 



1900b — Plethobasus Simspon, Proc. U. S. Nat. Mus., XXII, p. 764 



(As section). 

 1912b — Plethoba^s (Simpson) Ortmann, An. Car. Mus., VIII, pp. 



259-260. 



(Type, Unio aesopus Greene). 



Animal Characters: — Anarl separated from supra-anal 



