ùB JOHAN KIÆR. M.-N. Kl. 



Trilobitae. 



Fani. Eodiscidae Raymond. 



Weymouthia Raymond, 1913. 



The majority of authors employ the family name Microdiscus for this 

 interesting group of Lower and Middle Cambrian Trilobitae^. It has however 

 long been apparent that it would be difhcuk to retain this name, for 

 Emmons first employed it for a form that proved to be a young specimen 

 of a Tnmicleits. I agree with the view expressed by Raymond in his 

 little work "On the Genera of the Eodiscidae"-, and employ the family 

 name Eodiscidae for these forms. According to Raymond the famil3' com- 

 prises 3 distinct types, for which he gives separate names : Eodiscus 

 Matthew, Goniodiscus Raymond, and IVeymouthia Raymond. The last 

 named, with which we are here concerned, is distinguished by lacking 

 dorsal furrows both on the cranidium and on the pygidium. It thus reminds 

 one of the laevigahis group amongst Agnostidac. 



Weymouthia nohilis Yoku. 

 (PI. Ill, figs. 12, i2a-b|. 



1872. Agnosins .' nobilU F"ürd. Americ. Journ. Sei. 3 ter. page 419, figs. 1—2. 



1886. Aguoshts? »tobilis Walcott, Bull. 30 U. S. G. S. page 150, pi. 16, fig. 7. 



i86i. Agitosttts? )tobilis Walcott, roth Ann. Rep. U. S. G. S., page 629, pi. 80. fig. 7, 7a. 



1892. Microdisctts .' nobilis. Vogdes, Ann. Geol. 4, page 383. 



1913. Weytnoiithia Hobilis. Raymond, Ottawa Nat. Vol. 27, page 102 and 104. Figs. 15— 16. 



Description: The anterior border of the pygidium is straight, and 

 continues along the sides in angularly bent facets of articulation. In front 

 of the straight anterior border we see a comparatively narrow, facet of 

 articulation for the last segment. The lateral edges are evenly rounded, 

 and the posterior edge somewhat abbreviated. (?) We see a distinct, narrow- 

 marginal furrow, that is somewhat broader posteriorly ; presumably it marks 

 the doublure. The surface of the pygidium is even and comparatively 

 faintly arched (figs. 12a— a) without trace of axis or segmentation. 



Dimensi.ons: Length of Pygidium 3.3 mm. 



Breadth » — 4.4 mm. 



Breadth of the straight anterior border 2.8 mm. 

 Breadth of the facet of articulation ... 1.4 mm. 



* See e.g. P. Lake, British Cambrian Trilobites, page 30 (Pal. Soc. 1907). 

 2 Ottawa Nat. Vol. 27, page loi. 



