The; naiades of Missouri 121 



Sex Length Width Diameter Locality 



35 X 24 X 18 " — (White R., Hollister, Mo.) 

 cf 26 X 18 X 10 " — (Jack's Fork, Shannon Co.) 

 9 18 X II X 7.5mm — (Jack's Fork, Shannon Co.) 



The latter is a juvenile, tawny in color, with beak sculpture 

 extending well out upon the disk in undulated bars, showing 

 here, as in so many of the Anodontinae, that in the adolescent 

 shell there is more of tendency toward disk sculpture in the indi- 

 vidual, just as seen in the primitive shell of the whole race of 

 Naiades. 



Miscellaneous Remarks: — This species is easily identified 

 by its small shell (being never much more than an inch and one- 

 half long), by its slipper-shape and by its coarse concentric sculp- 

 turing. It is a great burrower and, although it may be abundant, 

 it may escape notice because of this habit. For this state calceolus 

 is only found in the streams of the south slope of the Ozarks where 

 it is found in company with its nearest relative Alas, marginata, 

 and is found in greatest numbers in Jack's Fork of the Current 

 River, Shannon County. It is found rather common in the streams 

 of Arkansas, and has a general distribution in the Ohio, Tennessee 

 and Cumberland Rivers; also the Lower and Middle St. Lawrence 

 systems. Being found with mature glochidia in late Fall it can 

 be classed as bradytictic. 



Alasmidonta marginata Say. 



("Nigger Toe," "Elk Toe.") 



PL XXIV, Figs. 78 A and B. 



1819 — Alasmidonta marginata Say, Nich. Inc., No. i. 

 1843 — Alasmidonta corrugata DeKay, Zool. of N. Y., Pt. 5, p. iQi< 

 PI. XXIV; fig. 259. 



ANIMAL CHARACTERS. 



Nutritive Sttructures: — Branchial opening densely papil- 

 lose; anal with fine papillae; supra-anal moderately separated 

 from anal, mantle-edges marked with squarish black blocks at 

 regular intervals; outer gills wider than inner; inner lamina of 

 inner gills connected with visceral mass; palpi very long and 

 united for one-half of their length antero-dorsad; foot very long 

 and powerful, orange colored; other parts tannish colored. 



Reproductive Characters : — Marsupium with wavy crowded 

 septa when sterile; greatly distended when gravid, bluish with 



