DIPS AS. 



VII. SUBGENUS DIPSAS. 1 



TRIANGULAR. 



Barhala bi-alata. Chenu. 

 TJnio bi-alata. Desh. Reeve. 

 Dianisolis Chinensis. Baf. 



Han. 



fOVAL. 



*discoideus. 6 Lea. 

 Symp. discoidea. Lea. 

 TJnio discoideus. Reeve. 7 Han. 

 TJnio tenuis. Gray? 

 An. tenuis. Gray? Baird & Adams. 

 An. Chinensis. Phili. 

 Barbala discoidea. Chenu. 



1 Mr. Swainson discards the name of dipsas, because it was used by Larentiui (1768) for a genus of 

 reptiles, and he says he gladly adopts that of Symphynota, Lea (Malac, p. 288). I think it better, how- 

 ever, that the rule recently adopted among most zoologists not to repeat generic names, should be more 

 prospective than retrospective, if adopted at all. Well and long established names are not likely to lead 

 to error. But the name of Barbala, Humphreys, has no doubt the pre-eminent title, and should take 

 precedence over all other proposed names, viz., Barbata, Sow., Cristaria, Schum., Appius, Leach, Diani- 

 sotis, Raf., Dijisas, Leach (1815), Symphynota, Swain, not Lea, Dipsax, Yoight, if we allow the names of 

 Humphreys. 



2 Perfect specimens show the whole linear tooth, and the folds on the posterior slope and on the 

 posterior wing, but old and imperfect specimens sometimes exhibit neither. The imperfect figure and 

 description by Leach (who made the genus in 1815) of this fine shell, led me to believe that it could not 

 be the same with that which I described under the name of Syin. bi-alata. 



3 Fide Dr. Gray. 



4 Dr. Dunker, in Cassel, showed me a valve in his collection from Siberia, somewhat fractured, 

 which is undoubtedly the Dipsas jylicatus, Leach. It is the largest specimen belonging to this family 

 which I have seen: in breadth about 12 inches; length Tj inches. See note on An. gigantea. 



5 Mr. Rafinesque, in the continuation of his Monograph (p. 7), affirms decidedly that the Symphynota 

 bi-alata, Lea, is a peculiar genus, but he changes it to Dianisolis Chinensis ! ! 



6 The posterior termination of the tooth shows some disposition to duplication, and evidently inclines 

 to pass into the subgenus Unio. 



7 The figure No. 275 is not discoideus, Lea, but probably taken from U. Isevissimus, Lea. 



8 In Griffith's Cuvier. 



