548 



NORTH AMERICAN INDEX FOSSILS. 



to the central nodes of the R, from which proceed ridges up the 

 brachials. Differs from T. inornatus in the more depressed inter- 

 brachial areas and perfectly flat tegmen. 

 Niagaran of Illinois and Wisconsin. 



LV. Lampterocrinus Roemer. 



Calyx unsymmetrical, elongate. IB anchylosed into a spread- 

 ing cup. B 5, large, four equal and angular, the posterior higher 

 and truncated. R very large. Costals two, the second supporting 

 an arm and the distichals. Brachials from distichals up forming 



o 



o 



a 



om 



q9j 



Fig. 1877. 



Lampterocrinus Unnesseensis. Calyx slighty reduced and 

 analysis. (After Roemer.) 



with the covering pieces a rigid tube from which small arms 

 branch at intervals. Interbrachials large, passing uninterruptedly 

 from the dorsal cup into the tegmen. Tegmen asymmetrical, 

 strongly bulging posteriorly and supporting a large, central anal 

 tube. Column pentangular. 



Differs from Siphonocrinus in the arm structure. Siluric. 



156. L. tennesseensis Roemer. (Fig. 1877.) Siluric. 



Plates convex, ornamented with radiating ridges dividing the 

 surface into deeply impressed areas. 



Niagaran of Tennessee. 



