NATURAL CLASSIFICATION OF THE TRILOBITES 149 



interest as being homologous with similar lobes in many 

 of the Lichadidse and Acidaspidse, where they often become 

 very conspicuous. In all the Proetidse the oblique lobes of 

 the fourth annulus of the glabella are also important in this 

 connection, as here again is marked the inception of side 

 axial lobes, which become prominent features in higher 

 genera, indicating greater specialization of the organs and 

 appendages of the head. 



Family VIII. BRONTEID^E Barrande. 



Dorsal shield broadly elliptical. Cephalon less than one- 

 third the entire length; glabella rapidly expanding in front, 

 with faint indications of lobes. Free-cheeks larger than the 

 fixed-cheeks. Facial sutures extending from the posterior mar- 

 gin just behind the eyes abruptly inward around the palpebral 

 lobes, and then diverging and cutting the antero-lateral margins 

 separately. Eyes crescentic. Thorax of ten segments, with 

 ridged pleura. Pygidium longer than cephalon or thorax; axis 

 very short, with radiating furrows* extending from it across the 

 broad limb toward the margin; doublure very wide; margin 

 generally entire. Ordovician to Devonian. 



Including the single genus Bronteus Goldfuss ( Goldius de 

 Koninck). 



Many of the species of Bronteus (as B. angusticeps 

 Barrande, B. palifer Beyrich) show a breaking up of the 

 glabella into symmetrically disposed separate lobes, as in 

 Conoliclias and Acidaspis. The frontal lobe is transverse and 

 much larger than the others. Back of it may be simple 

 grooves marking the elements (#. campanifer Beyrich), or 

 there may be one or two circular or elliptical swellings on 

 each side of the axis (B. angusticeps Barrande), or, in addition, 

 the axial portion may consist of several lobes. The reduction 

 of the axis of the pygidium and the expansion of the limb 

 meet with their greatest expression in this genus. Lichas 

 shows the decline of these characters, the pygidial limb 

 becoming more or less deeply lobed, and finally the lobes are 



