NEW SPECIES OF 13 11 A C II I 0 P 0 D A. 



585 



STR0PIIOD0NTA (?) COSTATA. (N. S.) 

 (Tab. III. a, fig. 5.) 



Specific character. — Shell minute, hardly three-eighths of an inch in diameter; regularly semicircular; 

 eleven prominent ribs like those of a modern pecten ; ventral valve nearly flat; dorsal slightly convex. 

 From the Davenport Limestone of Iowa, of Devonian date. 



STROPIIODONTA IOWENSIS. (N. S.) 



Specific character. — The limestones of Pine Creek, Iowa, of Devonian date, furnish another species of 

 Strophoclonta of a lenticular form, not figured in this Report, smaller than fig. 14 ; convex valve only 

 flatly arched; surface with delicate radiating strice, with about four concentric lines of increase. Width, 

 seven-eighths of an inch ; depth, three-fourths of an inch. 



ORTHIS CUNEATA. (N. S.) 



(Tab. III. a, fig. 10.) 



Specific character. — Shell wedge-shaped, circumference semicircular ; both valves about equally convex ; 

 surface nearly smooth ; with fine striae only visible with a magnifier. Nearly half an inch wide, and four- 

 tenths deep. 



From limestones near New Buffalo, Iowa, of Devonian date. 



SPIRIFER IOWENSIS. (N. S.) 

 (Tab. III., fig. 1.) 



Specific character. — This species approaches in form to D. mucronatus of the New York Reports, but 

 has fewer ribs ; only ten or eleven on either side of the mesial fold ; the sulcus is wider and not so deep ; 

 concentric lines of growth but little apparent ; the decorticated portion of the shell shows a slightly undu- 

 lating surface on the ribs. Length, one and a quarter inches ; breadth, two and a quarter. 



From the shell-beds of the Iowa River, of the age of the Hamilton Group of New York. 



SPIRIFER PENNATUS. (N. S.) 

 (Tab. III., figs. 3 ami 8 (?).) 



Specific character. — This species is remarkable for the great extension of the cardinal area, terminating 

 in produced angles or wing-like appendages, so that some specimens of this shell are nearly five inches 

 from angle to angle. Cardinal area very wide, more than half an inch. On each side of the sulcus there 

 are twelve distinct ribs, and five to six obscure ribs on the produced angles. Not imbricated by con- 

 centric lines of growth, as in the attenuated varieties of D. mucronatus (fig. 3, Nos. 4 and 5 Hall's New 

 York Report). 



From the shell-beds of the Iowa River. 



SPIRIFER LIGUS (N. S.) 

 (Tab. III., fig. 4.) 



Specific character. — This Spirifer is nearly as much produced at the angles as the last species, but the 

 cardinal area is comparatively narrow, which character especially distinguishes it from the preceding 

 species, as well as the greater number of ribs, which amount to twenty-six or twenty-seven, on either side 

 of the bourrelet ; the ribs are also more undulating, and have longitudinal strias ; this latter character, 

 together with the more triangular form of the whole shell, and its greater convexity, separates it from the 

 D. meclialis of the New York Reports. 



From New Buffalo, Iowa, in the shell-beds cotemporaneous with the Hamilton Group of New York. 



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