Section IV., 1884. [ 99 ] Trans. Eoy. Soc. Canada, 



V. — Illustrations of the Fauna of the St. John Group continued: on the Coiiocoryphea, 

 with further remarks on Paradoxides. By G. F, Matthew, M.A, 



(Read May 23, 1884.) 



In continuing my work on the Fauna of the St. John group, I have, at intervals dur- 

 ing the past year, made an examination of a part of the numerous species of trilobites 

 grouped by the late Prof C. F. Hartt ixuder the genus Conocephalites of Barrande. During 

 the examination of the fossiliferous material from the beds of Division Ic of the St. John 

 group necessary for this purpose, some points in illustration of the characters of the 

 Paradoxides described in my former paper were noticed, which were not observed when 

 that paper was written. To these I shall refer before entering upon the main subject of 

 this article, 



I.— PARADOXIDES. 



1. — Paradoxides Acadicus. {Fig-. 1.) 



Young of this species. — In trimming some pieces of slate, two heads of very young indi- 

 vidiials were exposed, which show important differences from the adult. These heads 

 were of equal size, and being only half of the length of the smallest head described in my 

 former paper, show the appearance of the species at a much earlier period of growth. The 

 length is about 4 mm., and it possesses in an exaggerated degree the wide-spread anterior 

 border which is a somewhat marked feature of the 8 (t.T) mm. size. This 4 mm. size is 

 also remarkable for the sharp Anopolenus-like sinus in the facial suture, and for the long 

 eye-lobe, which on the one hand touches the glabella, and on the other nearly reaches the 

 posterior margin. The cheeks are expanded to correspond to the spreading anterior border, 

 and the third and fourth furrows are placed very near the anterior end of the glabella. 



Pygidium {Fig. 2). — A tail-piece, 4 mm. long, appears to have belonged to a larger test of 

 this species. It is ovate in outline and has jjeculiarities not observed in any other. The 

 axial lobe is somewhat more than half of the whole length. It consists of two segments : 

 the anterior one ring-like and narrow, with a small lunate portion, one third of its length, 

 marked otf on the posterior side ; the posterior segment of the axial lobe is subtriaugular, 

 its extremity is rounded and the sides are rounded forward at the anterior c^iiarter. Along 

 the front and side of the lateral lobe of the pygidium there is a marginal fold or border, 

 which at its anterior end connects with the first ring of the axis. 



Sculpture. — The tipper surface of the pygidium is finely granulate, and in the posterior 

 half, where (in the specimen) the upper surface is broken off, the inner side of the under 

 surface presents a number of irregular parallel striae, concentric to the axial lobe and the 

 front of the pygidium. This tail-piece, both in its granulated surface, its thickness, and 

 its well preserved form, possesses characters belonging to the rigid test of Paradoxides 

 Acadicus. 



