BY R. ETHERIDGE, JUN., AND JOHN MITCHELL. 315 



and semi-imbricating. Similar sculpture exists in Proetus decorus, 

 Barrande,* but the Trilobites do not otherwise agree. The 

 normal number of ten thoracic segments is here departed from in 

 favour of nine, a character which P. bowningensis possesses in 

 common with the Bohemian species P. sculptits, Barr.,f and the 

 American Devonian P. longicaudus. Another peculiarity exists 

 in the rather long genal spines, which extend to and include the 

 fourth thoracic segment, a feature which is, however, exceeded by 

 some Bohemian species, as well as by P. latifrons, McCoy, £ and 

 one Australian form, P. australis, nobis. In P. latifrons, the 

 genal spines reach as far as the sixth thoracic segment. 



P. bowningensis does not closely resemble in its general specific 

 characters any of the numerous Bohemian species, having too 

 conoid a glabella and far too triangular a pygidium. Proetus 

 parviusculus, Hall,§ of the Hudson River Group, is much like our 

 PI. xxv. fig. 1c. about the glabella, and generally in regard to the 

 whole cephalic shield, but the outline of the pygidium is much too 

 semicircular. 



From P. Rattei, nobis, the present species is distinguished by 

 the absence of the longitudinal sulci on the glabella of that form, 

 and from P. austrcdis by the almost circumscribed condition of 

 the basal lobes. The large plain glabella and wide diverging 

 genal spines separate the Victorian P. euryceps, McCoy, || from our 

 species at once. 



Individuals from the Middle Trilobite Bed of the Bowning 

 Series have a more prominent thoracic axis than those from the 

 Upper Trilobite Bed, whilst the specimens obtained from the latter 

 horizon have not been observed to possess anastomosing ornament. 



* Syst. Sil. Boheme, 1852, Ir, Atlas, t. 17, f. 13. 



t Syst Sil. BohSme, 1852, I., Atlas, t. 15, f. 1 



+ Forhe.ua, Brit. Pal. Foss., Fas. 1, 1851, p. 174. 



§ Hall and Whitfield, Report Geol. Survey, Ohio, II., Pt. 2, Pal., 1875, 



p. 109, t. 4, f. 18. 



|| Prod. Pal. Vict., Dec. III., 1S76, p. 17, t. 22, f. 10, 10a. 



