CRIXOIDS AND BLASTOIDS. 105 



small, and apparently short. There are generally also two or 

 three interaxillaries. and frequently a small interbrachial between 

 the arm ba- 



Summit plates larger than their surrounding pieces and nodose, 

 but smaller than in allied forms. The central plate and proxi- 

 mals, although distributed with the usual regularity, are com- 

 paratively small. 



The ornamentation gives to this species a beauty which is 

 not surpassed by any other Actinocrinus. The plates of the 

 calyx are comparatively thin, and the suture lines difficult to 

 distinguish : they are not convex, but their surface is marked 

 by a system of sharply elevated, very prominent ridges, pass- 

 ing from plate to plate, meeting in large stellate clusters on 

 the interradial spaces. The ridges follow the middle of the radial 

 series, they are very conspicuous, and pass without interruption, 

 from the basi-radial suture into the arms, increasing a little in 

 width toward the arm bases. There are also bead-like elevations, 

 definitely arranged over the plates, and sometimes surmounting 

 the ridges. The sculpturing formed by this combination of 

 ridges and beads is very remarkable and constitutes a most 

 interesting feature of the species. 



Column round, composed of joints alternating in size; edges 

 of the internodal joints sharp, the intermediate ones rounded 

 and crenulated. A similar crenulate structure is found around 

 the projecting rim of the basals, giving it a resemblance to a 

 stem joint. 



Geological position, etc.: Kinderhook beds of the Lower Car- 

 boniferous, LeGrand, Marshall County, Iowa. 



Our own collection. 



Af.TINOORIXrS XODOBRACHIATUS (nOV. Sp.) W. & Sp. 



PI. XV, Fig. 5. Specimen with arms, from the anterior side. 



PL XVI, Fig. 10. Specimen without arms, from the posterior side. 



Of the type of Actinocrinus proboscidalis Hall, but with a 

 larger number of arms, which are less robust, and ornamented 

 on the back with conspicuous nodes, of which no trace is found 

 in the Burlington species. It also resembles our A. ornatisxi- 

 mus. especially in the arm structure, but the nodes are dis- 



