538 DESCRIPTIONS OF NEW TWO TEILOBITES^ 



glabella, but the shortness of this and the great width of the limb distinguish it 

 from that gToup. Other difficulties in the way of placing it with PhilUpsia are 

 its small eyes and their gTeater distance from the glabella. In its pygidial 

 features generally, but especially in the ornamentation of this part, it resembles 

 most closely some pygidia of Braclvymetopus. In the absence of the fine glabellar 

 furrows, it possesses the most important generic feature of Griffithides, but it 

 lacks the pyriform and gibbous-fronted glabella; its wide limb, short glabella, 

 eyes faceted and sub-distant from the glabella are also difficulties in the way of 

 placing it with this group. With the Braeliymetopi, perhaps, it agrees in a. 

 greater number of specific features than it does with the members of either of the 

 two other genera referred to above. The bead-like pustulation of its glabella 

 and pygidium strikingly resembles that found on Br. strzeleckii McCoy, Br. oura- 

 licus De Verneuil and Br. maccoyi Portlock. Its cephalic border agrees very 

 closely in shape axid ornamentation with the borders of the first and last of the 

 tliree species just referred to. Near the anterior and posterior inner angles of 

 the eyes it bears very pronounced tubercles, similar to two borne in identical 

 positions by Br. strzeleckii and, in part, by Br. ouralictus. Its short cylindrical 

 glabella, wide cephalic limb or border, and small prominent reniform eyes dis- 

 tant from the glabella are features characteristic of the Brachymetopi. The 

 genal spines, too, are like those of Br. maccoyi. Its small, pustulate basal lobes 

 of the glabella and its occipital lobe are very similar to the like parts of several 

 species of Brachymetopus. 



If the pygidium of the trilobite now under discussion be compared with the 

 pygidia of the two species Br. ouralicus and Br. strzeleckii referred to above, 

 it will be found that it agrees with each of them in most of its details — the 

 ornamentation of its test generally, the equality of the anterior spread of the 

 axis and the side lobes, in having nearly the same number of rings in the axis 

 and pleurae in each of the side lobes, the same kind of pustulation on the space 

 between the end of' the axis and the posterior edge of the margin. This latter 

 feature is one which I have noticed on no pygidia except on those now referred 

 to, belonging to the genus Brachymetopus, so that, simple feature as it appeai-s 

 to be, it is one of some significance. When the characteristics of our new trilo- 

 bite, detailed above, are considered in conjunction with the generic characteristics 

 of the three Carboniferous genera of trilobites, also compared and contrasted 

 with it in the text above, the difSeulty of referring it to either of those genera 

 will, I think, be admitted, for these characteristics consist of a very remarkable 

 blending of the generic characteristics of all three, those belonging to Brachy- 

 metopus (European type) preponderating. But for the absence of the fine 

 glabellar furrows, it might be placed in the genus PhilUpsia, as a very abnormal 

 species. Except that its glabella is not pyriform and its eyes are small, faceted 

 and subdistant from the glabella,, and for the relatively great width of the border 

 of the cephalic shield, a place for it might be found in Griffithides. Further, 

 there seems only one feature possessed by this trilobite which stands in the way 

 of placing it with Brachymetopus, and that is the presence of facial sutures; and 

 it may be noted here that there is evidence that the process of fusion of the 

 fixed and free cheeks had begun and the obsolescence of the facial sutures was 

 in process of accomplishment, for the majority of the head-shields found have 

 the free cheeks in place, yet the symphysis was not completed and the sutures 

 remain and must be reckoned with. Some writers on trilobites seem to regard 

 these sutures as having generic importance, but others, not less eminent, have 

 not so regarded them. For example, in the genus Acidaspis, species which have 



