223 



The enfolding of the crust on the lower side extends up- 

 wards about three fifths of the length of the tail and is 

 strongly but distantly striate. Surface marked with moder- 

 ate sized pustules and a few hollow spines. 



This species differs from L. Boltoni of New York in the 

 short broad head, prominent eyes, and in the tail having 

 only four points instead of six. It resembles L. {Platynotus) 

 trentonesis as recognized in the blue shales of Cincinnati, 

 Ohio, in the prominent eyes, but the head is much shorter in 

 proportion to its width, and the tail is broader and much 

 straighter on the anterior margin. 



Lichas Boltoni. 

 var. occidentals {Hall). 



A species of Lichas, resembling L. Boltoni of the Niagara 

 group of New York, occurs with the preceding species at 

 Waldron. The pygidium is the only part which has been 

 seen : in this the axial lobe in its upper part is prominent 

 and strongly defined at the sides, rounded below, and some- 

 what distinctly separated from the extension of the same in 

 the flattened border. The margin is deeply laciniate and 

 the processes thick and strong. The surface is very strongly 

 pustulose or verrucose in some parts. 



In the L. Boltoni the laciniations are much shorter and 

 wider, while the axial lobe tapers gradually into the border. 

 The annuiations of the upper part of this lobe are likewise 

 more distinctly defined than in the Indiana specimens. 



All the specimens from New York are in soft shale, while 

 the western forms lived on a more calcareous bed, occur- 

 ring in the thin limestone bands associated with the calca- 

 reous shale. The form and proportion of the pygidia differ 

 but little except in the depth of the laciniations. 



