THE NAUTILUS. 



VOL. XXI. SEPTEMBER, 19O7. No. 5. 



NOTES ON SOME EXOTIC UNIONID.E, 



BY L. S. FRIERSON. 



The collation of some private notes upon The Synopsis of the 

 Naiades by Mr. Chas. T. Simpson called my attention to several 

 errors in this great work. In the Synopsis Mr. Simpson dealt not 

 only with a great number of species, but with an enormous mass of 

 references to an involved and difficult literature. The following 

 notes are therefore offered in no unduly critical spirit. 



UNIO GIGAS (Swainson) Sby., U. CUMINGII Lea. 



Page 608, Mr. Simpson places (it is true, somewhat in doubt) as 

 a synonym of Tritogonia tuberculata, Barnes, the figure of Unio gigas, 

 Swainson (Sowerby, in Conchologia Iconica xvi, 1867, Plate LVI, 

 fig 287). 



This really fine figure has been totally misunderstood by both Mr. 

 Simpson and Mr. R. E. Call, the latter having more than once re- 

 ferred it to Unio multipiicatus Lea. It is probable that the habitat 

 assigned the shell by Sowerby the Ohio river is responsible for 

 these singularly poor determinations. Mr. Lea was not much mis- 

 led by t^e habitat, for in his synopsis he placed it among the for- 

 eign shells, and in his scheme of classification he placed U- gigas im- 

 mediately next to his Unio cumingii. The fact is that gigas is 

 only an adult cumingii. The type of the latter was a shell not one- 

 third grown, and hence only slightly resembling a full-grown speci- 

 men. 



