100 G. F. MATTHEW: ILLUSTEATIONS OF 



2. — Pabadoxides lamellatus, Hartt. {Figs. 3 and 4.) 



Through the kindness of Mr. J. F. Whiteaves, of the Greological and Natural History 

 Survey of Canada, I was afforded an opportunity of examining a well-presented head of 

 the typical form of this species. Prof. Hartt speaks of this trilobite as " a small species 

 distinguished from several others found with it by the presence of a number of sharp per- 

 pendicular laminae on the anterior lobe of the glabella." As it is desirable, for the purpose 

 of comparison with other species, that a more complete description of this trilobite should 

 be given, I have sketched the following characters : — 



The anterior margin is arched around the front of the glabella, and thence to the 

 suture it is straight. The flat area is one and a half times longer in front than at the 

 suture. The fold is much wider at the suture than in front of the glabella. 



The glabella is about one quarter longer than its width. It is narrowed and depressed 

 at the back, but rises anteriorly into a well-rounded dome. 



Glabellar furrmos. — The first crosses the glabella and is deeply impressed, especially 

 in the outer third, and arches back from both extremities to the middle of the glabella. 

 The second furrow fails to cross the glabella by about one-fifth of its width ; it is mirch 

 narrower than the first, and is deeply impressed ; it inclines backward as it ascends the 

 slope of the glabella, and the extremities of the segments are sharply bent backward 

 where they approach the axial line. The third and fourth furrows are lightly impressed 

 and are directed forward ; the third furrow extends about one-third across and is slightly 

 bent backward at the inner end ; the fourth furrow extends only about one-fourth across. 

 Neither the third nor the fourth extends qu.ite to the edge of the glabella. 



The occipital ring is somewhat inclined forward at the extremities, and is strongly 

 arched vertically. It is high behind and slopes gradually to the occipital furrow. This 

 furrow is deeply impressed in the outer third of its length, and in this part is' strongly 

 arched forward towards the middle of the first glabellar furrow. Between the outer 

 thirds there is a flattened area on the axis of the glabella where this furrow blends with 

 the first glabellar furrow, but the latter furrow is here somewhat the deeper. 



The posterior margin is broken in the specimen examined, but appears to arch down- 

 ward strongly at the extremity. The furrow is of regular width, and is moderately 

 impressed. 



The fixed cheek also is broken, but appears to be rather narrow ; it is elevated in the 

 middle and depressed at both ends. The ocular lobe in the specimen examined is broken off. 



Sculpture. — The anterior marginal fold is traversed by fine parallel raised lines, which 

 branch at intervals ; they are roughly parallel to the anterior margin, near which they 

 are more crowded. The front of the dome of the glabella is ornamented v/ith two or 

 more continuous sharp, raised ridges (separated by the space of about one millimetre) 

 which sweep around the front of the glabella on each side to the fourth furrow ; higher 

 on the dome of the glabella are small, broken and irregular ridges ; similar small, elongated 

 elevations of the test are scattered on the slopes of the glabella between the second and 

 fourth furrows. The projecting part of the occipital ring and the back of the dome of the 

 glabella are covered with tubercles, which, on the less elevated parts of the ring, and the 

 posteriorhalf of the glabella, gradually diminish in size, until they pass into granulations. 

 Similar granulations are found on the fixed cheeks. 



