ijo the; naiades of Missouri 



Miscellaneous Remarks: — In the young shell of the last 

 measurement the beaks were sculptured with inverted V-shaped 

 ridges similar to that of stihrostrata. This species is only found 

 in the Black River for this State. Rev. Wheeler considers lienosa 

 as intergrading with nigerrinia and while the two are usually found 

 in the same locality yet nigerrima 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 suhrostrata 

 but can be separated on account of an insufficient development of 

 mantle edge antero-ventrad to branchial opening. 



Eurynia (Micromya) iris (Lea.) 



("Rainbow Shell.") 

 PL XXVII, Figs. 97 A and B. 



1830 — Unia iris Lea, Tr. Am. Phil. Soc, III, p. 439, pi. IX, fig. 18. 



1898 — Lampsilis iris Baker, Moll. Chicago, Pt. I., p. 105, pi. XIII, 

 fig. I; pi. XIV, fig. 2. 



1912b — Eurynia {Micromya) iris (Lea) Ortmann, An. Car. Mus., 

 VIII, p. p. 341 and 342. 



animal characters. 



Nutritive Structures: — Branchial opening densely papil- 

 lose; anal crenulated; supra-anal large, closely connected to 

 visceral 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-looped ridges; epidermis 



