THE NAUTILUS. 103 



Tapes decussatus L. A distinct species. 

 Tapes floridus Sow. Two examples. 

 Venerupis iris L. A Mediterranean shell. 

 Donax trunculus L. 



Donax vittatus Lam. Smaller than the former. 

 Solen vagina L. Ceratisolen legumen L. 



Mactra corallina L. Common. Lutraria elliptica Lk. Mrs. 

 Whishaw. 



Pholas dactylus L. Probably will be found living. 

 Loripes lactea L. Single valves. Divaricella divaricata L. 

 Tellina cumana Costa. Not uncommon on mud flats. 

 Tellina distorta Poli. Rarely found. 

 Tellina planata L. One specimen. 

 Pandora inaequivalvis L. Mrs. Whishaw. 



THE ANATOMICAL STRUCTURE OF CERTAIN EXOTIC NAIADES COM- 

 PARED WITH THAT OF THE NORTH AMERICAN FORMS. 



BY DR. A. E. ORTMANN. 



Having studied the anatomy of the soft parts of a large number of 

 North American Uhionida, I published a preliminary account of the 

 results some time ago (NAUTILUS, Feb. 23, '10, p. 114 ff.). This 

 had the effect that several exotic genera were submitted to me for 

 examination, on which I have reported also (Parreysia, in NAU- 

 TILUS, April 23, '10, p. 139; Spatha, ibid., August, '10, p. 39). 



The peculiar facts discovered in these shells induced me to select 

 some representative forms out of the large material of South Ameri- 

 can mussels in possession of the Carnegie Museum, and collected by 

 Mr. J. D. Haseman, since a comparison of these with the others was 

 much needed. A superficial examination revealed at once some 

 very interesting features, and so I made up my mind to condense the 

 chief results in the present paper, and to give the necessary figures 

 to illustrate them. 



Of North American types I have used for comparison the genera 

 Margaritana, Quadrula and Unto. Margaritana stands by itself, 

 exhibiting some quite unique features. Quadrula and Unio (together 

 with Rotundaria and Pleurobema) are the most primitive forms 

 among the rest of the North American Unionidee, constituting my 



