656 THE LOWER SILURIAN PERIOD. 



parallel to the margin. This groove widens at the point where it 

 bends to go forward along the sides, in such a way as to encroach on 

 and thin out the marginal fold, and, just before reaching the anterior 

 margin, it narrows itself from the inner side so as to cause the lateral 

 lobes to widen somewhat anteriorly. These are narrow, flattened, 

 about half as wide as the middle lobe, narrowing to a point just 

 behind the middle lobe where they do not unite. The medial lobe is 

 about five-sixths of length of pygidium, shield-shaped, flattened, convex, 

 more elevated than the lateral lobe. Its anterior border is slightly 

 concave in the middle. The lateral angles are rounded, and the lobe 

 is conti'acted a little anteriorly. It is bounded by two deep and 

 well-marked furrows, which join one another in the middle of the 

 marginal furrow, forming a pointed arch.* Medial lobe projecting 

 farther forwards than the lateral ones. A little spine is situated on 

 its mesial line about one-fourth its length from front. Surface smooth. 



The pygidium and cephalic shield, from which the above descriptions 

 were drawn up, were collected by my father and myself at St John, 

 near the residence of W. R. Burtis, Esq., from shales of the lower 

 part of the Acadian gi'oup. They were associated with Conoce- 

 phalites Baileyi and C Matthexvi, Orthis Billingsi, etc. The two 

 parts are separate, and each is represented by but a single specimen. 

 I have little hesitancy in referring the one to the other. The 

 glabella seems to be marked by a broad but faint transverse depres- 

 sion just behind the anterior glabella furrow. There are indistinct 

 traces of an anterior articulating border to the pygidium. Both the 

 specimens figured are casts. 



Agnostus similis, Hartt, MS. Differs from the last species in its 

 straight sides, wider marginal groove, and more distinct marginal 

 fold. Cheek-folds narrower in front of glabella. The pygidium shows 

 similar difference of proportion. Ratcliff"e's Millstream, somewhat rare. 



Paradoxides lamellatus, Hartt, MS. This is a small species dis- 

 tinguished fi-om several others found with it by the presence of a num- 

 ber of sharp perpendicular laminae on the anterior lobe of the glabella. 

 Fig. 230.— Portions of Heads 0/ Paradoxides. 



* More so than in the figure. 



