[MATTHEW] STUDIES ON CAMBRIAN FAUNAS 85 



are closely crowded, both on the free cheek, and on the middle piece of 

 the head-shield ; along the genul spine the raised lines run diagonally 

 downward from the outer to the inner margin ; along the posterior 

 border of the head-shield there are crowded raised lines, as along the 

 anterior border. On the doubleur the lines are crowded and more dis- 

 tinct. The edges of the ring of the rachis show similar crowded wrinkles ; 

 on some pleurœ there is a narrow band, or transverse wrinkling on each 

 side of the pleural groove ; in others the wrinkled band covers the whole 

 under surface, and the wrinkles or raised lines become gradually drawn 

 out in V-shaped lines along the pleura, so that towards its extremity they 

 become parallel to the axis of the pleura. On the pygidium there are 

 raised lines, but finer and more crowded, and parallel to the posterior 

 border. 



Size. — Length of the middle piece of the head about 70 mm. 

 Width in front 110 mm. ; at the eye-lobe 95 mm. ; at the posterior angle 

 about 90 mm. Length of the cord of the anterior extension of the facial 

 suture 25 mm. ; of the ej^e-lobe 17 mm. ; of the posterior extension about 

 20 mm. Length of glabella and occipital ring about 55 mm.; width at 

 third farrow 25 mm. ; at the first furrow 32 ram. Length of movable 

 cheek 60 mm. ; and with genal spine about 175 mm. ; width at the front 

 25 mm. ; at the back of the eye-lobe 37 mm. ; at the posterior margin 

 about 35 mm. Length of the pygidium about 20 mm. ; width 27 mm. 



Horizon and locality. — Occurs in a very fine, greenish-gray shale, 

 resting on volcanic ash rock, seen in a railway cutting at Manuel's Station, 

 Conception Bay, Newfoundland, What appears to be the original sur- 

 face of the ash rock in Cambrian time was uneven, and the fine mud of 

 the shale settled into the inequalities of the surface. Almost directly 

 upon the old rock surface, there is a layer of a few inches of shale 

 abounding with the detached parts of this trilobite ; the tests are con- 

 fusedly crowded together, flattened and somewhat distorted in the shale, 

 and are accompanied by Myolithes Hathewayi. 



On comparison with Mr. "Walcott's section on Manuel's Brook, (a 

 short distance to the north) ^ I find no volcanic rock mentioned, hence I 

 suppose the rock on which the bed of shale rests that contains M. magni- 

 ficus, belongs to the older Intermediate, or Huronian system. To the 

 east of the ash rock are Nos. 3 and 4 of Mr. Walcott's section, hence it is 

 presumed that No. 5 corresponds in position to the volcanic ridge, as a 

 shore deposit, and that the bed of shale with M. magnificus will be at the 

 bottom or near the bottom of No. 6 of Walcott's section. Here, it is 

 stated, the head of an Olenellus was found. 



This fine species shows many points of resemblance in a general way 

 to Holmia Brdggeri, Wale, but there can be no doubt it is distinct, if 

 only by the fact that it has movable cheeks. The genal spines and 



1 U. S, Geol, Surv. Bull, 81, pp. 260, 261. 



