73. CONTRIBUTION TO 



The calix has a peculiar pinched look between the arm bases, the fold thus 

 formed being thrown into sharp cross ridges. 



There are sixteen arm bases, but the groups are not separated by notica- 

 ble depressions, the pinched appearance of the inter-arm areas giving an almost 

 unbroken rim-like appearance to the peripheral region. 



The vault is low, convex and rounded, made up of small, slightly tumid 

 plates, without apparent surface ornamentation. The central dome plate has a 

 small node, as also a plate above each arm group to the right and left of the 

 anal region. The anal opening is eccentric, but the vault is broken in about it, 

 rendering further description impossible. 



The respiratory pores are two to the arm opening and are small slits. 



This species belongs to the Depressus group, but may be readily recognized 

 by the ornamentation, continuous peripheral rim, low, almost smooth dome, 

 short, expanding calix, and the strong ornamentation of the small plates be- 

 tween the arm bases. 



It is from the upper Devonian beds near Charlestown, Ind., and the type 

 is in the collection of Mr. G. K. Greene. 



M AGISTOCRINUS UNICORNIS, N. Sp., (Rowley). 



Plate 24. Fros. 11, 12-13. 



The region of the basals, first radials and parts of the second radials form 

 a shallow concavity, bordered by a rounded zone. The calix is low and ex- 

 panding rapidly to the arm region. The number and arrangement of the calix 

 plates much as in the others already described, and nearly related species and 

 varieties. 



Arm bases of strongly lobed groups, the openings being sixteen in number, 

 and slightly directed upward. 



The ornamentation of the calix is quite obliterated in silicification, but 

 probably consisted of low radiate lines. Plates flat. The vault is low, some- 

 what inflated at the center, but depressed at the arm lobes. Plates numerous, 

 small, hardly convex near the center, but more pronounced about the ambu- 

 lacral ridges. 



The central dome plate spinose, and the eccentric anal opening looks like 

 the base of a short proboscis, or is something more than a mere opening through 

 the test. 



The low, rapidly expanding calix, strongly lobed arm groups, single central 

 dome spine and strongly defined anal opening will readily serve to identify 

 this little species. 



From the upper Devonian, near Charlestown, Ind., and the type is in Mr. 

 G. K. Greene's colleciion. 



