207 



from the base to the summit, and its greatest width at the 

 arm bases about the same. 



The genus Turbinocrinus of Troost differs from Melo- 

 crinus in having tho first plate of one of the interradial 

 spaces (or the first anal plate) truncating one of the basal 

 plates, which does not occur in an) 7 known species of Me- 

 locrinus. The structure of Turbinocrinus above the basal 

 plates is similar to Actinocrixus, differing from that genus 

 only in the presence of four basal plates. 



GENUS MACROSTYLOCRINUS (Hall). 



In the second volume of the Palceontology of New York, 

 published in 1862, I proposed the name Macrostylocrinus 

 for a crinoid having three basal plates, and five rays of 

 three plates each, from which proceed the arms, the inter- 

 radial series consisting of about five plates. In 1860 Dr. F. 

 Roemer has proposed Cytocrinus* for a crinoid of precise- 

 ly the same structure and of similar form. The latter, 

 though published eight years later has the advantage of 

 being a more euphonious name. 



The genus Ctenocrinus of Bronn, as described by Pictet, 

 possesses a structure resembling, or identical with Macros- 

 tylocrinus and Cytocrinus, though the exterior character 

 is very distinctive. For the present I preserve the name of 



MACROSTYLOCRINUS. 



MACROSTYLOCRINUS STRIATUS (Hall). 



Body depressed turbinate, calyx to the summit of the first ra- 

 dials being of a hemispheric form. The rays from the 

 second radials are spreading, the interradial spaces de- 

 pressed or not expanding beyond the upper edge of the first 

 radial plate. The basal plates are comparatively large; 

 first radials large, prominent in the middle near the upper 



* Silurische Fauna des Westlichen Tennessee, page 4, tab. 4, fig. 2a, 2b, 

 and 2c. 



