No. 89.] 



Ill 



ORTHIS OCCASUS(n.s.). 



Shell suborbicul'ar, the transverse greater than the longitudinal diameter; hinge- 

 line greater than half the entire width of the shell. Surface marked by numerous 

 fine tubular radiating striae, and a few. imbricating lines of growth. The length 

 and width of the dorsal valve are about as seven to nine. 

 This species resembles 0. vanuxemi and 0. penelope of the Hamilton group of 



New-York; but the dorsal valve is more gibbous, and the hinge-line proportionally 



longer. 



Geological formation and locality. In the Goniatite limestone; at Rockford, 



Indiana. 



RHYNOHONELLA (EATONIA) OBSOLESCENS ( n.s.). 



Shell short, subpyramidal, ventricose; anterior end truncated by a broad shal- 

 low sinus; sides rounded in the middle. Dorsal valve much the more gibbous, 

 regularly rounded in the middle, and somewhat abruptly elevated towards the 

 point. Ventral valve depressed convex towards the beak, becoming flattened and 

 concave in the middle, and abruptly bent upwards on the anterior half of the 

 shell; beak short and rounded, with the apex truncate. Surface of the upper 

 part of the shell smooth or finely striated : a few short obsolete folds upon the 

 mesial fold and sinus, while the margins of the shell appear to be crenulate on 

 the inner edge. 

 The shell has much the aspect of Eatonia; but the muscular impression, so far 



as can be ascertained from an imperfect cast, is that of Rhtxchonella. 



SPIRIFER SEMIPLICATA(n.s.). 



Shell pyramidal : dorsal valve moderately convex, the mesial fold affecting only 

 the anterior half : ventral valve much elevated; beak incurved over the foramen; 

 area short, undefined at the margins; mesial sinus well defined. Surface marked 

 by rounded slightly elevated plications, reaching about half way to the beaks: 

 entire surface marked by undulating lines of growth. Length from one-quarter 

 to one-half an inch or more. 

 In the young state, this shell resembles an Amboccelia; but the semiplicate 



character is a distinguishing feature. The form approaches Ctrtia; but the beak 



is rounded iind incurved over the area, which, having no defined margins, differs 



conspicuously from the species of that genus. 



Geological formation and locality. In the Goniatite limestone; Rockford, 



Indiana. 



SYNBATHOCRINUS OWENI(n.s.). 



Body calyculate, rounded below and gradually enlarging to the summit of the 

 radial plates : base short, truncated below by the large round column, distinctly 

 pentangular above by five radial plates which are wider than high. Surface gra- 

 nulose. 

 The base of this species is larger and more rotund than any of the Carboniferous 



species described. 



Geological formation and locality. In the Goniatite limestone at Rockford, 



Indiana. 



