THE NAIADES OF MISSOURI A33 
MISCELLANEOUS REMARKS:—In the young shell of the last 
measurement the beaks were sculptured with inverted V-shaped 
ridges similar to that of subrostrata. This species is only found 
in the Black River for this State. Rev. Wheeler considers lzenosa 
as intergrading with nzgerrima and while the two are usually found 
in the same locality yet nzgerrima is more likely to occur as a 
creek form. The writer obtained some gravid August 29 with late 
embryos. The young one of the above measurement was gravid 
and, as preserved, shows many characters like that of subrostrata 
but can be separated on account of an insufficient development of 
mantle edge antero-ventrad to branchial opening. 
Eurynia (Micromya) iris (Lea.) 
(‘Rainbow Shell.’’) 
PR XXVIT, Figs..07.A and: B. 
1830— Unio iris Lea, Tr. Am. Phil. Soc., III, p. 439, pl. IX, fig. 18. 
1898—Lampstlis iris Baker, Moll. Chicago, Pt. I., p. 105, pl. XIII, 
HES Folk SIONS alee 
1912b—Eurynia (Micromya) iris (Lea) Ortmann, An. Car. Mus., 
Nahi p Mp eign and 342° 
ANIMAL CHARACTERS. 
NUTRITIVE STRUCTURES:—Branchial opening densely papil- 
lose; anal crenulated; supra-arfal large, closely connected to 
viscera] mass; palpi small, one-half connected antero-dorsad; 
color of soft parts dark tan with posterior part of gills and mantle 
blackish. 
REPRODUCTIVE STRUCTURES:—Marsupia composed of twenty 
closely crowded ovisacs occupying post-half of outer gills; inner 
mantle edge fringed with eight or ten papillae, the most anterior 
ones reaching well toward the center of ventral edge where they 
are larger, postero-curved and terminating in small low papillae 
near the branchial opening—all rather wide apart; glochidia 
rather large, subovate measuring 0.240 x 0.300 mm. 
SHELL CHARACTERS. 
EXTERNAL STRUCTURES :—Shell small, elongate-elliptic, thin, 
dorsal line slightly curved, ventral straight; compressed anteriorly 
inflated in center of post-umbonal ridge; beaks pointed but low, 
sculptured by seven or eight double-Jooped ridges; epidermis 
