MIOCESTE MOLLUSCA AND CRUSTACEA. 137 



occupied by six radii on one, there are ten in the other; one of these has 

 the striae strongest on the narrow end and the other on the broad end. 

 There are equal variations in the arcuation of the back of the shell, and in 

 the size and the form of the fissure. The general outline of the base in its 

 elongate-ovate form is perhaps the most constant feature of the species. 

 Considering the degree of variation it is not surprising that there should be 

 some discrepancy between the two descriptions quoted from Mr. Conrad, 

 written at different times and probably from different individuals. 



Formation and localities : The species has been recognized from the gray 

 marls at both Shiloh and Jericho; and in the stony layers near Bridgeton 

 and in the brown clay near Shiloh, N. J. In collections from Rutgers Col- 

 lege, the National Museum, and the Academy of Natural Sciences at Phila- 

 delphia. 



Order TECTIBRANCHIATA. 



Family TORNATELLIDiE=ACT^ONIDiE. 



Genus ACTION Montfort. 



Action Shilohensis, n. sp. 



Plate xxiv, figs. 15-17. 



Shell of about medium size, subglo.bular or broadly ovate, the trans- 

 verse diameter being to the height about as three to five; spire short, the 

 apical angle about 70 degrees. Volutions six, short in the spire, abruptly 

 rounded on the top, giving an almost impressed suture line, and pre- 

 senting a step-like appearance to the spire, rounded and full below; 

 aperture moderately large, somewhat effuse below, the outer lip sharp; 

 columella short and the fold very distinct and defined. Surface polished, 

 with nearly equidistant impressed lines, except on the upper third of the 

 height or on the exposed portion in the spire, where they are obsolete; 

 lines generally clean, or free from punctse or dots. Some of the interspaces 

 on the lower part of the volution marked by an intermediate finer line. 



This species differs from several forms known in the Eocene formation 

 in being more globular, and in having a shorter spire. 



Formation and locality: In the gray marls of the Miocene at Shiloh, 

 N. J. From the collection of the National Museum. 



