124 PEOCEEDINGS OF THE MALACOLOGICAL SOCIETY. 



Genus Migranaja, n.gen. 

 Unio (sp.), Lamarck, 1801 {Unio littoralis, Lam.). 



Type,, Unio littoralis, Lamarck. 



Shell of moderate size, averaging 50 ram. in length, sub-solid, 

 ovate-elliptical, crassiform, rounded in front and behind, umbones 

 broad, elevated, and marked by numerous rather fine wavy ridges, 

 which extend out on later growth, grading into obsolete chevrons ; 

 two lateral and two pseudo-cardinal teeth in left valve and one each 

 in right, the pseudo-cardinals clavate, stumpy, and lying obliquely 

 transverse to hinge ; habitat lacustro-fluviatile. 



The present group, which does not seem to have been heretofore 

 distinguished from t/nio, but differs obviously in the form of the hinge- 

 teeth and early growth of the shell, has a distribution, considering 

 both fossil and recent records, from Eastern Oregon to Spain, equalled 

 in the Naiades only by Margaritana^ Unio, and Anodonta. 



MiGKANAJA COXDONI (White). 



Unio Condoni, AVliite, 188o. 



Shell large for genus, similar in outline to littoralis, but distinguish- 

 able by the broader, more inflated umbonal region ; hinge essentially 

 the same, but cardinal teeth heavier; liabitat apparently lacustrine. 



Oligocene : local freshwater beds in upper portion of John Day 

 formation, Oregon. 



Genus Anodonta, Lamarck. 



Ili/tilus (sp.), Liune, 1758 {M. cygneus, L.) ; Anodontites (sp.), 

 Bruguiere, 1792 (J/, cygneus, L.) ; Afiodonta, Lamarck, 1799 

 (i7/. cygneus, L.); Anodon, Oken, 1815 (emended form); 

 Anoduntes, Cuvier, 1817 (emended form); Brachyanodon,^ 

 Fischer & Crosse, 1893 {A. coarctata, Anton = A. impura. Say). 

 Type, Mytilus cygneus, Linne. 



Shell of moderate size, averaging 50 mm. in length, anodontiform, 

 thin, broadly ovate, ovate-elliptical, or elongate-elliptical, compressed 

 or inflated, beaks barely elevated above general curvature of shell, 

 and marked by low calycules and a varying number of fine wavy 

 knotted ridges, hinge edentate and gently curved; adolescent growth 

 broadlv ovate, alate and compressed ; habitat lacustrine and lacustro- 

 fluviatile. 



Anodontites of Bruguiere has recently been revived for the present 

 group without, in the writer's opinion, good cause. The name appears 

 to have been originally intended for all the edentate Naiades of 

 Europe and elsewhere. Mytilus cygneus and anatinus are mentioned, 

 but the first species, and the only one described, is the South American 

 A. crispata, a species of Hyriinae. In 1799 Lamarck, doubtless 

 aware of Bruguiere's group, proposed Afiodonta for the European 

 species, thus incidentally restricting Afiodontites to the single South 



' With one or two others from the ' Mission Scientifique Mexique ' omitted 

 from the Zoological Record. 



