I'l.VTK I.XXXIV— C'oiitiimed. 

 StUOI'IIOMCLLA COSTATULA, S)). MOV. 



Fig^s. 1"), It'i. Dorsal and pi'dtile views nt' tlie slicU ; .sliinving' tlie reveitteil convfxily nf tlii- vulvex iiml tin- 

 sharply rouiuled, irref^iilarly diclidtoniizing' |. ligations. 

 Niaffara tfi'(Hi|>. £,(iiii.sinllt', Kentiuky. 



Had'inesquina alteknata. Coiintd. 



Fig*. 17, 18. Enlargements of unibonal portions of internal rast.s of the peiliile-valve. to»how the Kllin|{' of 

 the pedicle-passage. In tig. 18, which represents the older shell, this tillini; is wen to be the 

 smaller and is constricted at its liasi;, evincing thus the tendency of the shell to close thin pax- 

 sage at its inner extremity. X 3. 



Hudson River grouji. lirratic blockx in xcestent Nmo York. 



PrODUCTELLA NAVICELLA, Hall. 

 See Plate 17. 

 Fig-. 19. A .small pedicle-valve preserving the spines in a perfect condition and showing (he convergent- 

 of the cardinal spines. X 5. 



Hamilton group. Caiiandaigua Lake, New York. 



Strophalo.sia Rockfordkxsi.s, sp. IIOV. 



See Plate 17a. 

 Figs. 20, 21, 22. Ventral, dorsal and cardinal views of a specimen ; showing the general external characters 

 and the umbonal cicatrix 



Upper Devonian. liarkfard, Iowa. 



Plectambonites prodocta, sp. IIOV. 



Figs. 23, 24, 2.^. Cardinal, jirohle and front views of an internal cast of a pedicle-valve ; showing the form 

 of the teeth and muscular impre.ssions, the short hinge and the gi-eatiy pi-oduced anterior 



margin. 



Niagara dolomites. Yellow l^prings, <)hU>. 



Hyattef.la conoesta, Hull. 

 See Plate 40. 

 Figs 2(i-28. Doi'sal, front ami profile views of one of the original specimens (Palicontology of New York, 

 vol. II. pi. xxiii, tigs. 1, f, g, i). 



Clinton group. Monroe county, New York. 



Spirifer l.en'is. Hall. 



See Plate 38. 

 Fig. 29. A portion of the cardinal region enlai-ged to show the peculiar structure of the deltarium, which 

 bears a circular perforation with elevated margins, anil is surrounded by an elongate, smooth 

 area, at the edges of which the growth lines are sharply interrupted. X 3. 



Chemung gi-oup. Near Ithaca, New York. 



.•^E.MINUI.A .'iUBQUADRATA. Hall. 

 See Plate 47. 

 Figs. 80, 31 . Dorsal and profile views of the original specimen. 

 Kaskasia limestone. Chester, Illinoli. 



Cliotiiyris ROYSSII, L6veille. 



Fig. 32. The interior of a brachial valve ; showing the form of the hinge-plate. 

 Coal Measures. Tournal, Belgium. 



Athyris concextrica, von Biicli. 

 Fig. 33. An enlargement of the hinge-plate ; showing its form, tripartite division, and apical perforation. 

 Middle Devonian. Ferques, Brittany. 



