BY R. ETHERIDGE. JUN., AND JOHN MITCHELL. 175 



ments equal in width to side lobes, from sixth segment diminishing 

 gradually, well preserved specimens with a row of three or more 

 granules on each segment, no dorsal spine observed ; pleurae 

 straight and fiat to fulcrum, distal ends sharply deflected and 

 slightly separated, deeply grooved, grooves terminating short of 

 the extremities, the posterior facets of each pleura with a row of 

 granules, of which that on the fulcrum is most prominent and 

 persistent, appearing on the pleurae of the pygidium also, axial 

 furows conspicuous. Pygidmm small, strongly granulated ; axis 

 small, consisting apparently of three segments, divisions of the 

 pleurae the same, axial furrows distinct; margin thickened. 



Ohs. — This is rather a minute Trilobite, the largest of our 

 specimens not exceeding three-eighths of an inch, and it is diffi- 

 cult to determine the exact number of thoracic segments ] but we 

 believe ten to be correct. 



The distinctive features of this species are its ovoid and tumid 

 glabella, very tumid cheeks, granulated ornamentation of the 

 whole test and particularly of the glabella and free cheeks, small 

 eyes, flatness of the pleurae between their proximal ends and the 

 fulcrum, and their shortness from the fulcrum to the distal ends. 

 It differs so widely from the other species described in the present 

 paper that comparison is unnecessary. 



In some specimens the granules of the glabella are arranged in 

 tolerably regular longitudinal rows, in others this is not so con- 

 spicuous. The normal shape of the eyes we believe to be round or 

 subconical ; but our specimens show them of various shapes. In 

 the larval form the eye is very small, and the specimens are almost 

 invariably in a rolled state. 



This very peculiar form of Cyphaspis is allied to C. cerberics, 

 Barr.,* and C. Davidsoni, Barr.,f by reason of its subcrenate 

 anterior cephalic border, but in both the species named tlie 

 border becomes absolutely serrate, while our best preserved speci- 

 mens are only faintly so. Still more closely resembling our 



* Syst. Sil. Boheme, 1852, I. p. 489, t. 18, f. 49-51. 

 t Syst. Sil. Boheme, 1852, I. p. 489, t. 18, f. 54-56. 



