PLATE I— Continuoil. 

 LiNGULA QUADRATA (EicllWilld), Hall. 



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

 which is frequently more strongly developed, and the projection of the umbonal region of the 

 pedicle-valve beyond the apex of the brachial. The prominence of the .latter feature is to some 

 degi'ee due to the displacement of the valves. 



Ti'enton limestone. Trenton Falls, N. Y. 



LiNQULA lOWENSIS, Ovveil. 



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

 developed median septum, the well-detined central scars (h), and the progi'es.sive laterals (x). 

 Natui-al size. ■• 



Galeiia'linieaione. Fountain, Minnesota. 



LiNGULA SPATULATA, VuiUlXeni. 



Fig. 15. A pedicle-valve (?), retaining the shell, and showing evidence of a median septum in the umlional 

 region. X 6. 



Genesee slate. Canandalgua Lake, N. Y. 



LiNGULA COMPTA, Sp. UOV. 



Fig. 16. A specimen of the brachial valve (?) ; showing the latei'al impressions and the median septum ex- 

 tending to the anterior margin. X ?. 



Hamilton shales. Canandalgua Lake, iV. Y. 



LiNGULA COMPLANATA, WilliillllS. 

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

 Portage group. Ithaca, N. Y. 



LiNGULA sp ? cf. Cuyahoga, Hall. 



Fig. 18. A pedicle-valve, retaining a portion of the shell-substance, and showing the position of the lateral 

 scars. X 2. 



Chemung group. Panama, N. Y. 



LiNGULA ANATINA, LiUlliirck. 



Fig. 19. The interior of the pedicle-valve ; showing the character of the muscular scars and septa as they 



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

 Fig. 20. Bi'achial valve of the same. Natural size. 

 Recent. Philippine Islands. 



LiNGULA Elderi, Whitfield. 



Figs. 21, 22. Copies of the lithographic figures given by Mr. Whitfield (Geol. Surv. Wisconsin, vol. iv, pi. 27, 

 tigs. 4, 5), of the interiors of the pedicle and bi-achial \'alves, respectively. Drawn from a cast 

 which presei'ves the internal characters with remarkable completeness. X 2. 

 Trenton limestone. Near Rochester, Minnesota. 



LiNGULA cf. DENSA, Hull. 

 Fig. 23. The interior of a pedicle-valve ; showing the septum and lateral scars. X 2. 

 Hamilton shales. Centerfield, N. Y. 



DIGNOMIA, Hall. 



Page U. 

 DiGNOMIA ALVEATA, Hall. 



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

 lateral septa. Natui-al size. 



H.imilton shales. Fultonhatn, N. Y. 

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

 and distinct lateral septa. Natural size. 



Hiimilton shales. Canandaigiia Lake, N. Y. 



