NOTE TO THE TRILOBITA 



Throuffhout this paper the shorter dimension of the lobes of the 

 glabella, the occipital ring and marginal rim, as well as of the axial 

 rings and plenree of the thorax and pygidium is spoken of as their width- 

 This seems desirable, since in comparing them with the separating furrows 

 wi speak of their shorter demensions as the width of the furrow- Thus 

 the combined width of the glabellar lobes and farro\\s constitute the 

 length of the glabella, while the combined width of the axial rings and 

 furrows constitute the length of the axis of the thoi-ax, etc- The length of 

 the lobes consititutes the width of the glabella or thorax as the case may 

 be- It is thus the measurement along the longitudinal axis of the entire 

 animal, which constitutes the width of the lobes or rings of either ceph- 

 aloii or body. An exception to this is desirable in the case of the anterior 

 lobe of the glabella the longitudinal measurement of which may be 

 i?n.'atiir than the transverse. In Such cases, to avoid misunderstanding— 

 the measurement is further designated by the term antero-posterior or 

 longitudinal this referring to the longitudinal axis of the animal as a 

 whole- A few deviations from this rule have crept in, these being noted 

 in the errata* 



