AGNOSTUS FISSUS. 3 



and the lateral lobes of the tail behind the axis arc separated by an impressed lino 

 (in most species). 



(2) Laevigati. — Distinguished by the fact that the lines which should define the 

 glabella and the pygidial axis are effaced. Test always smooth and shining, some- 

 times with indications of furrows. The margin tends to vanish on the head, 

 whereas on the tail it remains broad. 



(3) Limbati. — This group is distinguished by the fact that the shields arc in 

 general more or less quadrate in form. The head has a broad margin. The basal 

 lobes are large. The cheeks in front of the glabella are not separated by any 

 groove, nor are they furrowed on the sides. The tail is commonly provided with 

 spines. 



(a) Begii. — Distinguished by its broad margin, the narrowness of the cheeks 

 and of the lateral lobes of the tail, together with the breadth of the glabella 

 (especially of the anterior lobe), and the shortness of the third segment of the 

 pygidial axis. 



(b) Fallaces. — In this section the head is narrower, the margin not so broad, the 

 cheeks large, the basal lobes tolerably large, and the third segment of the pygidial 

 axis is the longest. 



(4) Parvif routes. — This group is distinguished by its feebly developed glabella, 

 which is not lobed. 



Section Longifbontes. 

 1. Agnostus fissus, Lundgren MS. Plate I, figs. 1 — 3. 



1879. Agnostus fissus, Linnarssou, Ora faunan i kalken nied Conocorypke exsulaus, Sver. geol. 

 Uuders., ser. C, no. 35, p. 23, pi. ii, fig. 34. 



1880. Agnostus fissus, Tullberg, Om Agnostus-artema, Sver. geol. Uuders., ser. C, no. 42, p. 16, 

 pi. i, fig. 3 a — d. 



1896. Agnostus fissus, G. F. Matthew, Trans. N. Y. Acad. Sci., vol. xv, p. 230. 

 1896. Agnoskis fissiis, var. trifissus, Gr. F. Matthew, ibid., p. 231, pi. xvi, fig. 10. 

 1902. Agnostus fissus, var. perrugata, Gronwall, Bornholms Paradoxideslag, Danm. geol. Uuders. 

 II raekke, ur. 13, p. 50, pi. i, fig. 1. 



Head rounded, with a narrow margin. Glabella bilobed ; anterior lobe small, 

 subquadrate, rounded in front, where it is cleft by an impressed furrow; posterior 

 lobe slightly constricted a little in front of the middle, the anterior portion raised 

 centrally into a slight keel, which bears towards its posterior extremity ;i small 

 tubercle ; basal lobes small, triangular. Cheeks nearly equal in width throughout, 

 separated in front of the glabella by a slight furrow; surface ornamented by 

 irregular furrows which are often radiate. 



