718 SILUIUAN TRILOBITES, 



pleural spines and non-serrated secondary spines; the simple bi- 

 sjiiuate pj'gidium; prominent and clearly faceted eyes. 



INIany cephalons occur from which the cowl and spines have 

 separated, and left the occipital ring quite smooth and to all 

 appearance spineless. 



C. longispiiia attains a length of two and two-thirds inches. 

 The pygidium bears a very close resemblance to that of SelenopcHis 

 Bnchii, Barr., sp., in its spineless margin other than the axial 

 spines. 



The cephalon represented in PL Liv., fig. 2, possesses occipital 

 spines that exhibit a decided tendency to curl underwards, as do 

 tliose of Selenopeltis Biichii, Barr. More complete examples of 

 our form may determine the necessity of transferring it to Corda's 

 genus. 



Log. and Horizon. — Bowning Village, Co. Harden, Middle 

 and Upper Trilobite Beds — Bowning Series ( = Hume Beds, Jenkins, 

 and lass Beds, David). Co//.— Mitchell. 



EXPLANATION OF PLATES. 



Plate L. 



Odontopleura bowningexsis, E. and M. 



Fig. 1. — A nearly complete specimen, but with the genal spines wanting, 

 and the various portions of the cephalon undisturbed ( x 2^). 

 Coll. Jlitchell. 



Fig. 2. — A cephalon with one genal spine preserved ( x 3^). Coll. Mitchell. 



Fig. 3. — A cephalon somewhat distorted. Coll. Mitchell. 



Odontopleura parvissima, E. and M. 



Fig. 4. — A nearly complete example ( x 3). Coll. Mitchell. 



Fig. 5.— Portion of a thorax, and the pygidium ( x 4). Coll. Mitchell. 



Fig. 6.— Portion of a cephalon ( x 2^). Coll. Mitchell. 



Ouontopleura Rattei, E. and M. 



Fig. 7. — An almost complete example, with the central lobe of the glabella 

 removed, exhihiting the labrum in position ( x 3). Coll. 

 Mitchell. 



