FOSSILS OF THE BURLIXGTOX GROUP. 345 



ter toward their upper extremities. So far as can be seen, 

 the two outer arms of each ray are simple from their origin 

 on the secondary radials, and composed of a single series of 

 rounded and constricted pieces as far up as the last bifur- 

 cations of the other arms; consequently there appear to be 

 eight ultimate divisions, or arms, to each ray. (Vault un- 

 known.) 



Surface apparently minutely granular, and with a small, 

 more or less denned ridge extending from the base up the 

 primary radials to the third radial, on which it bifur- 

 cates and sends a branch to the base of each of the two 

 main arms. On the first radials, as well as the anals, there 

 is also some tendency to send off an obscure ridge across 

 from one to another, on' each side, ^one of the body plates 

 are tumid, though they are generally very slightly convex. 



Hight of body from bottom of base to the top of secon- 

 dary radials, 0.16; breadth, about 0.30 inch. 



This species is related to A. cliloris, Hall, but is much smaller, and 

 differs in having its body, below the arms, merely rather rapidly ex- 

 panding, with nearly straight sides, instead of being hemispherical. 

 Its arms also bifurcate differently. In the chloris, for instance, they all 

 (or at any rate the inner ones), after their origin on the secondary 

 radials, bifurcate once on the first piece beyond, while in our species 

 the inner arms bifurcate on the second piece, and the outer of those 

 subdivisions again on the second piece. 



Locality and position Upper division of the Burlington member of 

 the Lower Carboniferous, at Burlington, Iowa. Mr. WACHSJITJTH'S col 

 lection. 



AOTIXOCEIXITES. Section (5.) 

 ACTINOCRIXITES LOXGUS, M. and W. 



PL 8, fig. 1. 

 Actinocriniteg tongrtw, MEEK aart WOKTHKX. Proceed. Acad. Jfat. ScL, Phila., 1869, p. 156. 



BODY rather elongate-obconic below the arms, the sides 

 expanding gradually, with a moderately convex outline 

 from the base to the tertiary radial pieces, which, with the 

 brachial pieces, curve very slightly outward. Base about 



45 



