Notices respecting New Books. 379 



18. Unio patulus. — Testa ovata, compressd, cuneiformi, incequila- 

 terali, obliqud, transversa ; umbonibus compressis ; valvulis sub-crassis ; 

 natibus sub~terminalibus ; dente cardinali parvo ; laterali Longo et sub- 

 curvato ; margaritd albd. 



Hab. Ohio. T. G. Lea. My cabinet. Cabinet of T. G. Lea. Ca- 

 binet of Prof. Vanuxem. Diam. -8, length 14, breadth 2*3 inches. 



Genus SYMPHYNOTA. 



Testa Jluviatili, bivalvi ; valvulis superne connatis. 



Shell fiuviatile, bivalve ; valves connate at the dorsal margin 



Animal same as that of Unio. [?] 



Remarks. — Objections will most likely be made to the introduction 

 of a new genus into a family acknowledged already to be in great 

 confusion, and presenting many and various difficulties. The forma- 

 tion of the genus Symphynoia, it is hoped, will rather be conducive 

 to a diminution of that difficulty, by a division which all must acknow- 

 ledge to be as natural as any of those of the family. The distinctive 

 characteristic of this genus is the testaceous connection of the two 

 valves of the shell above the hinge. I therefore remove from the 

 existing genera all the connate shells without regard to the forms of 

 their teeth, believing, that should this family be hereafter remodelled, 

 it will present only two natural genera; one having a testaceous con- 

 nection of the valves, the other dispossessed of it. The difficulties 

 attending the adopted genera of the Na'iades> viz. Unio of Bruguiere, 

 Hyria, Anodonta, Iridina, Castalia* of Lamarck, Dipsas of Leach, 

 and Alasmodonta of Say, have been mentioned by two eminent En- 

 glish conchologists, W. Swainson and G. B. Sowerby, as well as in 

 America by P. H. Nicklin. Mr. Sowerby (Zool. Journ. vol. i. p. 55.) 

 has reunited them under the name of Unio, of which he makes two 

 great divisions. 1. Without teeth. 2. With teeth; and these are 

 each subdivided into " winged" and " not winged ;'" which are again 

 divided into the various forms of teeth, or the " hinge line." The 

 evident objection to this arrangement is the difficulty of deciding 

 upon the passage from the "not winged" to the "winged." Thus 

 we do not find the Anodonta trapezialis and Anodonta glauca, which 

 Lamarck describes as " compresso-alata,'' 1 mentioned among the 

 "winged," while we have " Anodon alatus of Swainson and La- 

 marck," which is not described in the " Hist. Nat. des Animaux sans 

 Vertebres f." 



It is evident that the apparatus for depositing the calcareous and 

 epidermidal matter on the elevated and connected wing must be differ- 



* This genus was placed by Lamarck in the family Trigoncea, certainly 

 with no propriety. It has been placed by Sowerby and Latreille among the 

 Naiades, and here must be considered as a species of Unio, and not a genus. 

 The observant M. de Blainville has placed Castalia and Hyria among the 

 Uniones, and Iridina and Dipsas among the Anodontce. Castalia ambigua is 

 undoubtedly a fiuviatile shell, and approaches most closely to the U. trian- 

 gularis. The teeth are those of the Unio, and it differs only in its longi- 

 tudinal furrows from the general characters of the Unio. 



f Sav describes his An. gibbosa as being alated. 



3 C 2 ent 



