NEW AGELACRINITES 



193 



shaped, with narrow, arched cover plates or 6) shorter and 

 broader, with broad and long cover plates; 3) the presence and 

 structure of a peripheral band either a) composed of few large 

 plates with very fine ones on the outer edge or h) broad with a 

 great number of small plates. 



So far as the generic names actually proposed are concerned, 

 they are found to embrace the before mentioned characters in the 

 following manner. 



Agelacrinites : thecal plates mosaic, irregular, sculptured 

 raps very long and narrow 

 peripheral band composed of large plates with 



very small ones at the margin 

 A. h a m i 1 1 o n e n s i s Vanux. 



Discocystis ( = Echinodiscus = Ageladiscus): thecal 

 plates mosaic, polygonal, smooth 

 rays very long and narrow 

 peripheral band composed of a few large plates 



with no fine ones outside of them 

 D. kaskaskiensis Hall 

 D. sampsoni Miller 



Lepidodiscus : thecal plates squamous 



rays very long and narrow 



peripheral band very narrow or extinguished, 

 composed of large and' small plates; the latter 

 few, the former projecting on the aboral surface 

 L. squamosus Meek 

 L. alleganius sp. nov. 



These generic names strictly construed, as they must be to 

 maintain a definite value, leave a commanding number of agela- 

 crinites without farther appellation. We do not zealously con- 

 tend for the value of such divisions among these later Agela- 

 crinites. If any fact is made clear by the foregoing observa- 

 tions it is that passage conditions from one to another of the 

 typical species of proposed genera of these bodies do exist in 

 such measure as to obscure the validity of the divisions. Never- 

 theless such terms may be used helpfully till our knowledge 



