BY R. ETHERIDGE, JUNR., AND JOHN MITCHKlL, 483 



appreciation of the characters used by Salter to distinguish C. 

 hlumenbachii from other forms, we are forced to change our views 

 and conclude that the Bowning species, though it has some char- 

 acters similar, is specifically different. Again, by a study of 

 Salter's description and figures of C. tuberculosa, we were im- 

 pressed with the similarity between the Bowning species and 

 this one, but failed to reconcile their identity. We had revealed 

 to us, however, by our study of the characters of these two 

 species, how fully the Bowning one possessed those of both, and, 

 in addition, has a fourth pair of glabella-furrows The attached 

 tabulation of the structural features of the three species will 

 show the resemblances and differences. A study of this tabula- 

 tion will establish the separation of our trilobite-form from the 

 other two, but there is a Bohemian species with which our 

 species must be compared, viz., Calymene incerta Barr.,* which 

 shows four pairs of glabella-furrows, and, in this important 

 feature, agrees with our form. The distance of the eyes from the 

 axial grooves, the highly thickened (pig-snouted) frontal margin 

 are common to the two forms; but in C. incerta Barr., the latter 

 is said to be straight in front, and continuing along the free 

 cheeks, becomes effaced at the genal angles. In our form, on 

 tlie other hand, the triickened border continues along the free 

 cheeks and round the genal angles, joining with the thickened 

 posterior borders of the fixed cheeks, and is always gently 

 curved or segmental in front. The proportion of length to width 

 is said by Barrande to vary much in his species, but, in our form, 

 these proportions are fairly constant. 



Comparing the thoraces of the two forms, we find, in C. 

 incerta, that the axis reaches the maximum spread at the fourth 

 ring; in ours, the neck-ring and the first five axial rings have 

 practically the same spread or width. Again, in C. incerta, the 

 axis is wider than the pleural lobes; in ours, on the other hand, 

 the axis is a little narrower than the pleural lobes. The axial 

 rings have their bases very nodular, but this feature in C. 

 incerta is inconspicuous. The rings of the axis in both agree in 



* Barrande, Syst. Sil. Eohenie, PL 19, figs. 30, 31. 



