PLATE I— Continued. 

 LiNQULA QUADRATA (EicluVilld), HuU. 



Fig. 13. A large example, from which much of the shell has l)een exfoliated ; showing the iiiediiin septum, 

 which is frecxuHiitly more sti-ongly ilevelopi'd, and the pi'ojection of the unibonal i-egion of the 

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

 degree due to the tlisplacement of the valves. 



Trenton limestone. Tn-nto?i Falls, N. Y. 



LiNGULA loWEXSIS, OvVCll. 



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 progressive laterals (x). 

 Natural size. 



(ralena limestone. Fountain, Minnesota. 



biiJ lUiJ: B-iJi-» LiNGULA SPATULATA, VillUlXCin. 



Kig. 15. A pedicle-valve (?), retaining the shell, and showing evidence of a me<li;iH .st-iilum in tin; umbonal 

 region. X 6. 



Genesee slate. Canandaigua Lake, N. Y. 



LiNGULA COMPTA, sp. IIOV. 



Fig. 10. A specimen of the brachial valve (?) ; showing the latei-al impressions and the median septum ex- 

 tending to the anterior margin. X 2. 



Hamilton shales. Caiiandaigua Lake, N. Y. 



LiNGULA COMPLANATA, WlllitUllS. 

 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, Ilitll. 



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

 scars. X 2. . . 



Chemung grouji. Panama, N. Y. 



LiNGULA ANATINA, Luilllirck. 



Fig. 19. The interior of the pedicle-\'alve ; showing the character of the muscular scai'S and sept.a .as they 



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

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

 Recent. PhHip2>ine Islands. 



LiNGULA Elderi, Wliitficld. 



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

 tigs. 4, 5), of the intei-iors of the pedicle and brachial valves, resjiectively. Drawn from a cast 

 which preserves the internal characters with remarkable completeness. X 2. 

 Trenton limestone. Near Rochester, Minnesota. 



LiNGULA Cf. DENSA, Hull. 



Fig. '28. The interior of a pedicle-valve ; showing the septum and lateral scars. X 2. 

 Hamilton shales. Centerfield, N. Y. 



DIGNOMIA, Hall. 



Page li- 

 DiGNOMIA ALVEATA, Hllll. 



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

 lateral septa. Natural size. * 



Hiimilton shales. Fultonham, N. Y. 

 Fig. 25. A portion of the interior of a large jiedicle-valve (0, with a shorter and broader median .septum, 

 and distinct lateral septa. Natural size. 



Hamilton shales. Canandaigua Lake, N. Y. 



