BRlTiSH FOSSILS. 



3 



tinguisliecl from the lateral and more forward portions ; these are 

 obliquely ovate, — the centre lobe is pyramidal. 



Tail nearly of the same shape as the head ; the margin furnished, 

 toward its hinder edge on each side, with a prominent tooth. The 

 axis is very broad and convex, somewhat clavate, and reaching 

 nearly to the margin, a space the width of the latter being left 

 between ; it is of greater breadth than the sides (even including 

 the narrow margin). The front pair of lobes are distinct, rounded- 

 triangular, and their own diameter apart ; the second pair (lig. 3, 4) 

 occupy a less width, are not very distinctly circumscribed, and are 

 divided from the large terminal lobe by a faint transverse furrov^^ 

 The tubercle on the intermediate pair is prominent but short ; it 

 scarcely invades the terminal lobe, and is of nearly the same shape 

 in all our specimens, however distorted. 



Variations. — Our larger specimens fig. 1, 4, (fig. 5 is magnified) 

 from the lowest and upper Lingula Flags have the axis of the tail 

 rather longer and somewhat more pointed than in fig. 3, but this may 

 be entirely due to elongation from pressure. The terminal lobe of 

 the glabella too is shorter in proportion in the former, but there 

 seems to be no other real diff*erence. The rugose veins which 

 ornament the limb are always conspicuous in well-preserved speci- 

 mens, but are much obliterated in less perfect ones, as our figures 

 will show. 



Affinities. — Compared with Angelinas incorrect figures of A. pisi- 

 formis and A. planiGauda (I have Swedish specimens of those 

 species before me), A. princeps has the axis of the tail (though 

 Angelinas figures have it too short) decidedly longer, and reaching 

 so far as to leave a space, between it and the margin, of only the 

 breadth of the latter ; and the tubercle, which Angelin represents 

 as elongated and reaching far down the middle of the axis in his 

 A. planicauda, is very short and prominent in our species. In 

 both these respects they agree better with Swedish specimens of 

 A. pisiformis than with Angelin's figure ; and if it were not for 

 the longer glabella and tail axis, the larger size and the decided 

 radiation of the limb in our fossil, we should have united ours with 

 the well-known Scandinavian form. Our second variety jS is more 

 like it than the first and more ornamented one, «. 



In size Agnostus princeps nearly rivals the largest of the 

 Swedish forms, A. reticulatus and A. aculeatus, Angelin, pi. 6, 

 fig. 10, 11. These, however, show a strong reticulation of the 



