NAIADES OF MISSOURI 5 1 



half profusely and irregularly pustulate to smooth ; beaks rather 

 high, moderately inflated sculptured concentrically but faintly; 

 epidermis dark straw to chocolate brown in color. 



Internal Structures :^Cardinals heavy, irregular, double 

 in each valve: inter-dentum broad, at right angles to laterals; 

 laterals heavy, double in left, single in right ; scars deeply impressed ; 

 umbonal cavities compressed by deep crevices; nacre usually white, 

 irridescent especially posteriorly. 



Sex Length Height Diameter Um. ra. Locality 



9 70 x 58 X 41mm 0.310 (Platte R., Agency, Mo.) 



c?' 60 X 50 X 30 " 0.300 (Grand R., Darlington, Mo.) 



Q 42 X 36 X 26 " 0.295 (Platte R., Claire, Mo.) 



<f 17 X 14 X 8 " 0.300 (Grand R., Utica, Mo.) 



Since schoolcraftensis is one of the greatest occurrence in 

 individuals for this state, the writer has been able to secure the 

 largest collection of its adolescent shells than any of the Naiades 

 in Missouri. The above latter measurement is that of the smallest 

 one but it was without hyssi. Its general outline is more elongated 

 than the mature shell, resembling the adult Q. quadrula, post- 

 umbonal ridge more prominent, beaks fuller, almost drawn back 

 to the center of dorsal line, characteristically painted with a 

 bright, broad, fan-shaped, green ray at base of post ridge within 

 the original shell area; beak sculpture indistinct, concentric, 

 broken anteriorly by a radiating furrow directed out on disk. 



Miscellaneous Remarks: — The differences of this variety 

 from the species has already been mentioned under the description 

 of the genus. This form was not admitted by Simpson as a race 

 and is merely referred as "a nearly smooth, compressed form of 

 piistiilosa." The varieties of typical ptistulosa, indeed, are great — 

 especially as to disposition of pustules, etc., but this larger more 

 characteristically quadrate form is so abundant in the north and 

 west, where pustMlosa-types are rarely found, that it surely deserves 

 a separation into the subspecific, if not specific class. According 

 to the figure and description that triangular variety found in 

 the Ohio River, (that is, Lea's pernodosa,) might be a synonym of 

 schoolcraftensis. Taking it all in all this subspecies is purely a 

 geographical race, but may pass into normal form in a few places, 

 even in the north and west, such as in the Mississippi River, 

 Illinois and local points where clear water and swift streams are 

 found. Schoolcraftensis is a lover of quiet, muddy situations, 



