182 THE AMERICAN MIDLAND NATURALIST 
except perhaps shorter laterals arranged at right angles to the 
interdentum. 
Sex Length Height Diameter Locality 
Cus ke SEX 4O, mm (MiGsh Re lea Grange) 
Q 56 x 56 x 34 ” ( ” ” ” ) 
ot 46 x 46 x 30 ” ( ” ” ” ) 
OU 20 a eXUin2 Taneexaul ONS tie (White ’’ Hollister) 
The latter measurement is of a juveniles from a lot identified 
by Mr. Frierson as approaching granzfera although would perhaps 
fall more under tuberculata. 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 granifera. 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 
eranifera 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 granifera—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 granifera 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—FPlethobasus Simspon, Proc. U. S. Nat. Mus., XXII, p. 764 
(As section). 
1912b—Plethobasus (Simpson) Ortmann, An. Car. Mus., VIII, pp. 
259-260. 
(Type, Unio aesopus Greene). 
ANIMAL CHARACTERS:—Anal separated from  supra-anal 
