SWALLOW — DESCRIPTION OF NEW FOSSILS. 85 



This fossil is common in the Archimedes Limestone of 

 Cooper county, Missouri. Collected by Dr. Giddings. 



Rhynciionella perrostellata. 



Shell elongate; wide and roundel in front; narrow, cylin- 

 drical, and elongate towards the beaks. Valves about equally 

 convex, contracted and semicylindrieal towards the beaks ; 

 the dorsal highest in front, and the ventral towards the beaks; 

 both convex along the middle, abruptly curved towards their 

 margins in front and on their sides, but sloping more gradu- 

 ally towards the junction of the lateral and anterior margins. 

 Surface of each valve marked with about eighteen simple, 

 sharp, radiating costae, which are obsolete near the beak (one 

 or two added by implantation). It is also ornamented with 

 fine concentric striae and distinct plications across the con- 

 tracted portions. 



Length, .75; width, .Crl; thickness, .48. 



This shell is very unique, and easily recognized by the con- 

 tracted prolongation of its valves towards the beaks. It was 

 collected by Dr. Giddings from the Archimedes Limestone of 

 Cooper county, Missouri; where it is associated with Ii. sub- 

 cuneata, Ii. arctirostrata, and T. sublanceolata. 



Spirifer translatus. 



Shell small, ovate, gibbous, ovate, widest below the mid- 

 dle, punctate, decussate. Ventral valve strongly arched, very 

 convex towards the beak; umbo large; beak strongly incurv- 

 ed over the area; sinus deeo and wide in front, obsolete 

 towards the beak, subangular in the bottom ; area small, tri- 

 angular; foramen rather small, triangular, equilateral ; cardi- 

 nal line short, length about one third the width of the shell. 

 Dorsal valve suborbicular, gibbous and scarcely arched from 

 the umbo to the anterior margin, flattened towards the late- 

 ral margins, raised into a rounded mesial fold in front with a 

 rounded sinus on each side, making the edges of the valves 

 sinuous; beak small, projecting a little beyond the cardinal 

 line, scarcely incurved. Surface ornamented with very fine 

 concentric and radiating stria?, small punctures, and lines of 

 growth. 



Length, .58; width, .51 ; thickness, .85. 



This Spirifer closely resembles the Spirigera formosa ; 

 but its area and imperforate beak separate it from that spe- 

 cies and genus. 



It is a rare i'ossil in the upper divisions of the Archimedes 

 Limestone near Chester, Illinois, and St. Mary's, Missouri. 



