TUIRTY-EIGIIT EMBllYONIC UNIONID.l-:. 47 



Unio penicillatus, Lea, fig. 5. Pouch-shape ; dorsal line short ; slightly rounded at the ends ; side mar- 

 gins flattened above and curved below; basal margin semi-circular; color clear white. Has no hooks. 

 Chattahoochee River, Georgia. 



Unio securis, Lea, fig. 6. Pouch-shape ; dorsal lino very short ; slightly rounded at the ends ; side mar- 

 gins flattened above and much curved below; basal margin nearly semi-circular; clear white. Has no 

 hooks. Cincinnati, Ohio. 



Unio retusus. Lam., fig. 7. Pouch-shape; dorsal line short; side margins flattened; basal margin nearly 

 semicircular ; clear white. Has no hooks. Cincinnati, Ohio. 



Unio Peatii, Lea, fig. 8. Pouch-shape ; dorsal line rather long ; side margins flattened above and curved 

 below; basal margin rounded ; clear white. Has no hooks.* lloswell, Georgia. 



Unio spatulatus. Lea, fig. 9. Pouch-shape ; dorsal line long ; side margins slightly curved ; basal margin 



rounded ; clear white. Has no hooks. Fox River, Illinois. 

 Unio LUTEOLUS, Lam., fig. 10. Pouch-shape; dorsal line rather long, nearly straight ; side margins flattened 



above and curved below ; basal margin nearly semicircular ; light brown. Has no hooks. Columbus, 



Ohio. 

 Unio rectus, Lam., fig. 11. Pouch-shape; dorsal line rather long; side margins arcuate ;f basal margin 



semicircular ; clear white. Has no hooks. Columbus, Ohio. 



Unio phaseolus, Hild., fig. 12. Pouch-shape ; dorsal line long, slightly curved outward and obtuse at the 

 ends ; side margins more curved below than above ; basal margin nearly semicircular ; clear white. 

 Has no hooks. Columbus, Ohio. 



Unio occidens. Lea, fig. 13. Pouch-shape ; dorsal line long, slightly curved outwards and obtuse at the 

 ends; side margins slightly flattened above and rounded below; basal margin nearly semicircular; clear 

 white. Has no hooks. Fox River, Illinois. 



Unio novi-Eboraci, Lea, tig. 14. Pouch-shape ; dorsal line long ; side margins nearly arcuate ; basal 

 margin nearly semicircular ; clear white. Has no hooks. Fox River, Illinois. In outline the three 

 last are very nearly alike. 



Unio OVATDS, Say, fig. 15. Pouch-shape; dorsal line short; side margins flattened above and rounded 

 below; basal margin nearly semicircular ; clear white. Has no hooks. Cincinnati, Ohio. 



Unio Woodwardianus, Lea, fig. 16. Pouch-shape ; dorsal line short, slightly curved outward and obtuse 

 at the ends ; side margins subarcuate ; basal margin semicircular ; clear white. Has no hooks. Fig. 

 16' represents a single sack about double the natural size. It is altogether different from the general 

 form of the sacks of other species, and will be described with the singularly organized branchial uterus 

 elsewhere. Etowah, River, Cass County, Georgia. 



Unio .multirauiatus. Lea, fig. 17. Pouch-shape; dorsal line short, slightly outwardly curved in the 

 middle ; side margins subarcuate, slightly flattened above ; basal margin semicircular ; clear white. Has 

 no hooks. Columbus, Ohio. 



Unio lioamentinus. Lam., fig. 18. Pouch-shape; dorsal line rather long, slightly outwardly curved and ob- 

 tuse at the ends ; side margins arcuate ; basal margin semicircular ; clear white. Has no hooks. Co- 

 lumbus, Ohio. 



* Taken from the branchial uterus apparently not quite perfect, 

 t 'I'lic fif^urc is rather too much flattened on the sides. 



