BY F. RATTE, ING. DES ARTS ET MANUP., PARIS. 101 



the furrows of the glabella are not apparent in our specimens, and 

 that the median part of the head seems also more slender, becoming 

 narrower as it reaches the globular projection. 



The great difi'erence is in the pygidium, which, although com- 

 posed of the same number of pleurae, is broader and has a nearly- 

 flat surface, and only shows the origin of appendages on the outer 

 margin,- where unfortunately the prolongations of these appendages 

 are broken (fig. 6). The dimensions of the last specimen are as 



follows : — 



Length 17 mm. 



Breadth 10 mm. 



Length of head 6^ mm. 



Length of pygidium IJ mm. 



Width of pygidium 3 mm. 



One specimen, (fig. 7) which was lent to me from the Depart- 

 ment of Mines for comparison, shows only the head, which is 

 10 ram. in length, corresponding to about 26 mm. for the total 

 length of the animal without the appendages of the pygidium, and 

 1.5 to 16 mm. in breadth. 



EXPLANATION OF PLATES. 



(Plate I). 



Diagrams of pygidia. figs. 1-6. 



Fig. 1. — Lichas hirsutui, Fletcher (= L. palmata, Barr.) Journ. Geol. Soc. 



1850, pi. XXVII. , bis, fig. 2. x 2. 

 Fig. 2.— Id. id. Loc. cit., pi. XXVIL, fig. 6. x 2. 

 Fig. 3.— Id. id. Loc. cit., pi. XXVIL, fig. 5. x 2. 

 Fig. 4. — Lichas palmata, Barr. Syst^me Silur. Bohem., pi. 28, fig. 1. 



Fig. 5. — Id. Loc. cit., fig. 9. This fig. is accompanied in Barrande's work by 

 the following remai'k : — " Pygidium isol^, dont I'axe est tr^s- 

 prolong6, et dont les tubercules spiniformes sont tres-d^veloppes 

 sur le contour. " x 2. 



Fig. G,— Lichas palmata var. sinuata. x 3. 



