PLATE I— Continued. 



LixGULA QUADKATA (Eichwakl), Hilll. 



Fig-. 13. A large example, from which much of the shell has been exfoliated ; showing- the median septum, 

 which i,s frequently more strongly developed, and the projection of the undional region of the 

 pedicle-valve beyond the? apex of the braehial. The prominence of the lattei- feature is to some 

 degree due to the displacement of the valves. 



Trenton lime.stone. Trenton Falls, N. T. 



LiNGULA loWENSIS, OwCll. 



Fig. 14. The interior of a brachial valve, probably referable to this species ; showing th(! conspicuously 

 developed median septum, the well-detined central .scars (h), ami the progi-e.s.si ve laterals (x). 

 Natural size. 



Gralena limestone. Fmmtain, Minnesota. 



LiNGULA SPATULATA, VilllllXem. 



Fig. 13. A peilie.le-valve (?), retaining the shell, and showing evidence of a median aeptnm in the iimbonal 

 i-egion. X 6- 



Genesee slate. Canandaigita Lake, N. Y. 



LiNGULA CO.MPTA, sp. IU)V. 



Fig. 16. A specimen of the brachial valve (?) ; showing the lateral imiires.sions ami the median septum ex- 

 teniiing to the anterior margin. X 2. 



Hamilton shales. Canandaiffiui Lake, X. Y. 



LiNGULA COMPLANATA, WllliaillS. 

 Fig. 17. The interior of a brachial valve; showing the fulcra of the lateral muscles. X 2. 

 Portage group. Ithaca, N. Y. 



LiNGULA .s|) ? cf. Cuyahoga, Hull. 



Fig. 18. A i)edicle-valve, retaining a poition of the shell-substance, and showing the position of the lateral 

 scars. X 2. . 



Chemung grouji. Panama, N. Y. 



LiNGULA anatina, Laniiiick. 



Fig. 19. The inteiior of the pedicle-valve ; showing the character of the muscular scai-s and sejpla .-u-; they 



appear when the musculai- bands and the mantle are wholly removed. Natural size. 

 Fig. 20. Brachial valve of the same. Natural size. 

 Recent. Philippine Islands. 



LiNGULA Elueri, Wliitficld. 



Figs. 21. 22. Copies of the lithographic tigures given by Mr. Whitfield (Geol. Sui'v. Wisconsin, vol. iv, pi. 27, 

 tigs. 4, 5), of the interiors of the pedicle anil brachial valves, lespectively. Drawn from a cast 

 which preserves the internal charactei-s with remarkable completeness. X 2. 

 Trenton limestone. Near Rochester, Minnesota. 



LiNGULA Cf. DENSA, Hall. 

 Fig. 23. The interioi- of a pedicle-valve ; sliowing the septum and lateral scai-s. X 2. 

 Hamilton shales. Centerfield, N. Y. 



DIGNOMIA, Hall. 



Page H. 

 DiGNOMIA ALVEATA, Hall. 



Fig. 24. A cast of a brachial valve ; showing the long, sharp median septum ami the fainter diverging 

 lateral septa. Natui-al size. ' 



Hamilton shales. Fultonham, N. Y. 

 Fig. 25. A portion of the interior of a large pedicle-valve (l), with a shorter and broailei' median septum, 

 and distinct lateral septa. Natural size. 



Hamilton shales. CanandaigiM Lake, N. Y. 



