62 



THE NAUTILUS. 



are pale, but are generally suffused with blackish. The gonads 

 are brown to red, mostly of a peculiar dull lavender color in 

 the female, and the latter color, or purplish brown, is the pre- 

 vailing color of the eggs and placentae. The charged gills be- 

 come thus rather dark purple, or purple-brown, shading some- 

 times to dull red or blackish, in other cases to brownish, 

 brownish pink, brick-red, or even pale brown. These are very 

 peculiar tints, by which this species is easily recognized in the 

 field: four marsupial gills of this blackish-purple color are not 

 known in any other Nay ad. 



Glochidia have been found only in specimens belonging to 

 the headwaters variety (barnesiana bigbyensis). They are subel- 

 liptical, slightly higher than long, L. 0.15, H. 0.16 mm. 



Although a true Fusconaia, this species (or group of forms) 

 stands isolated within the genus, in characters of the shell as 

 well as in the soft parts. It differs from the species of the 

 subrotunda-grou^ (incl. ebena, pilaris etc.) very markedly by its 

 smaller size and by the very shallow beak cavities. The forms 

 of the undidata-growp (incl. flava, and the cuneolus- and cor- 

 forms) have generally also somewhat deeper beak cavities, and 

 the shell has a more or less distinct posterior ridge, with a flat- 

 tening or a shallow groove in front of it, characters which are 

 missing in the bamesiana-group. As has been pointed out, in 

 the latter group, the color of eggs and placentae is remarkable: 

 in all other forms of Fusconaia, this varies from white to bright 

 red. 



I introduce here another species, in order to show that the 

 barnesiana-type is also represented outside of the Cumberland- 

 Tennessee drainage, namely in the Ozarks. 



Fusconaia ozarkensis (Call) 1887. 



F. ozarkensis Call, Pr. U. S. Mus. 10, '87, p. 499, pi. 27. 

 Tr. St. Louis Ac. 7, '95, p. 33, pi. 18. Lampsilis ozarkensis 

 Meek & Clark, Bur. Fisher. Doc. no. 759, '12, p. 18. Pleu- 

 robema utlerbacki Frierson, in: Utterback, Naiad. Missouri 

 (Amer. Midland Natural 4, 1916, p. 86, pi. 5, pi. 20, f. 63). 



I have specimens from James River, Galena Stone Co., Mo., 

 and White River, Cotter and Norfolk, Baxter Co., Ark., do- 



