1888.] NATURAL SCIENCES OF PHILADELPHIA. 247 



DESCRIPTIONS OF TWO NEW FOSSILS FROM 

 THE DEVONIAN OF IOWA. 



BY CHARLES R. KEYES. 



Conocardium altum nov. sp. (Plate XII, figs. 4a and 4b.) 



Shell of medium size, subtrigonal, anterior view broadly cordate* 

 Anterior end truncate, with a forward slope from the umbones to 

 the lower anterior sharply rounded extremity. Dorsal margin 

 behind the beaks slightly curved, with the edges of the valves 

 incurved, while in front of the beaks it is jiroduced forward into a 

 more or less prominent alate extension ; basal margin crenate within ;; 

 posterior extremity at the hinge line decidedly angular. Beaks 

 rather prominent, gibbous, incurved. Hiatus lanceolate ; occupying 

 about two-thirds of the lower posterior margin. Surface marked by 

 simple, regular, radiating costse, about forty in number, twenty-five 

 of which occupy that portion of the shell behind the umbonal slope ; 

 the umbonal slope is broad, bordered on each side by a prominent 

 icosta .which gives it a decided biangular appearance ; the costse are 

 crossed by numerous fine, crowded concentric lines; and a few larger 

 somewhat imbricated lines of gi'owth. 



Length 24 mm. ; breadth 21 mm. ; height 20 mm. 



Horizon and locality. Limestones of the Hamiltonian at lowai 

 City, Iowa. 



This species somewhat resembles certain forms of C. trigonale of 

 Hall, but the very broad strongly biangular umbonal slope readily 

 distinguishes it from that species. It also approaches some congen- 

 eric forms from the Devonian of Europe, especially certain species 

 from the western part of France, recently described by M. CEhlert^ 

 Cyrtoceras opimum nov. sp. (Plate XII, fig. 5.) 



Shell rather large, strongly curved, gradually expanding toward 

 the outer chamber, but enlarging more rapidly transversely than in 

 the opposite direction ; transverse section broadly elliptical, slightly 

 flattened on the ventral side. Distance between the septa about one- 

 fifth or one-sixth the transverse diameter. 



Horizon and locality. Hamiltonian of Johnson county, Iowa. 



This is a large and robust species from the Iowa Devonian, hav- 

 ing a length along the dorsum of probably forty or forty-five 

 centimetres, and a transverse measurement of eighteen or twenty 



1 Etude sur quelques Fossiles Devoniens de I'ouest de la France. 



