ON SOME NEW TRILOBITES FROM CANADIAN ROCKS. 231 



the Geological Survej^ of Canada, the specific name of Canadensis, as 

 originally bestowed on this trilobite by the author, has been retained- 

 Barrande, in the work just cited, allu'les to another American trilobite 

 in the possession of M.. de Yerneuil, but unnamed and unfigured, with 

 which our species may very possibly agree : only, the caudal shield of 

 this specimen would appear to possess no lateral segmentation, and to 

 have a scarcely defined axis, as M. Barrande refers it to the platycepha- 

 lus or gigas type.* His statement respecting it is as follows : — " Nous 

 avons vu recemment, dans la belle collection denotre ami M. de Verneuil 

 un Asaphus des Etats-Unis, qui, portant a Tangle genal une pointe 

 longue et grele, constitue une esplce tres distincte di As. {Is.) gigas. 

 Malheureusement, nous ne savons quel est le nom specifique qui lui a 

 ete donne par les savans Americains. Ce trilobite se rangerait dans 

 le group de A. gigas, d'apres les souvenirs qui nous restent de sa con- 

 formation." 



§ 2. Description of Asaphus Canadensis. This description is based 

 on what is probably the long or male form. 



General outline, a broad oval. Vertical to transverse diameter, nearly 

 as 3 : 2. Relative lengths of head-shield, thorax and pygidium, as 1 t 

 0.88: l.l. 



Head-shield obtusely pointed anteriorly, much as in Asaphus platy- 

 cephalus. Genal angles terminating in sharply-pointed horns of the 

 Paradoxidestype, extending downwards to about the middle of thebody.-f- 

 Facial suture, as shewn in the figure ; the branches uniting in an obtuse 

 but clearly defined angle above the glabella, nearly at the extreme an- 

 terior margin of the head-shield, and terminating at the lower margin, 

 about midway between the glabella and the genal angles. Glabella, 

 feebly raised, broad, and generally conformable at its upper part to the 

 outline of the facial suture. At its base, there occurs a slight but 

 evident neck-furrow. There are no furrows on the glabella itself. 

 Length of glabella to length of head-shield, as 0.8 : 1.0. Eyes, mo- 

 derately raised, and delicately reticulated ; although, in most specimens 

 they are more or less destroyed. Breadth between the eyes, to extreme 

 breadth of head-shield across them, as 5 : 11 , Whole surface of the 

 head-shield covered with fine punctures, except at the striated limb. 



Thorax, with eight segments. Axis well defined ; narrow, somewhat 

 broader in the middle than at the ends. Mean breadth of axis, to 



* It is perhaps the Asaphus lowensis of Dale Owen. 



t In most specimens, as in the figure, the horns extend to the bottom of the fourth thoracic 

 segment; but in a small specimen obtained quite recently from Whitby, and kindly sub- 

 mitted to us by Mr. J. P. Smith of Toronto, they reach to about the middle of the sixth 

 pleura. In oiu- figure they do not make a sufficiently sharp angle with the lower border of 

 the head-shield. 



