NO. 3 CAMBRIAN AND OZARKIAN TRILOBITES '/I 



extensions of the free cheeks remains on the dorsal surface well 

 within the edge. Finally, the eyes are not ' nearly halfway to the 

 front of the cephalon ' but wholly behind the midlength of the cra- 

 nidium. The hypostoma, when the anterior wings are entirely un- 

 covered, is much wider than long. In most other respects also it 

 resembles the hypostoma of Symphysunna, the only differences of 

 any consequence being that the anterior wings are more quadrate in 

 form and pointed at the outer front extremity, and the depression 

 at the middle of the anterior edge much shallower. 



" In none of the features mentioned is H. colUeana like H. aflinis. 

 They cannot belong to the same genus. So far as the cephalon is con- 

 cerned, the former is much nearer Ogygia corndensis, a British 

 Llandeilo Flags species figured by Salter in his monograph, and for 

 which Raymond ^ has proposed the new designation Ogyginus. The 

 similarity and apparent relation to the latter extends to the hypos- 

 toma ; but the neck and glabellar furrows, even though imperfectly 

 developed, together with a strongly segmented pygidium, are essential 

 characters of Ogyginus whose absence in the species collieana will 

 not permit its unqualified reference to that genus. As the peculiarities 

 of the latter species do not seem to be covered by any established 

 genus, the new generic term Belief ontia is proposed for it. 



"It is this Belief ontia collieana that is above referred to as a close 

 ally of Symphysurina. It seems to me a derivative of some species 

 of this genus, differing from its ancestors in the development of a 

 flat border in front of the glabella. At the same time, and perhaps 

 largely in consequence of the growth of the border, the facial suture 

 became intramarginal. These departures approximate to conditions 

 usually found in typical Asaphidae. But this seems a case of parallel 

 tendencies in the development of different lines and not one of 

 orthogenesis." 



Genotype. — Hentigyraspis collieana Raymond. 



Range. — Ozarkian : Mons formation. Alberta, Canada. Rocky 

 Mountains. Canadian : Stonehenge, Bellefonte, Pennsylvania. 



Observations. — This genus has many species in the Ozarkian and 

 so far as the studies have gone only a few pass into the Canadian. 

 The study of the group, however, is too little advanced to be altogether 

 certain of its complete range. 



' Raymond, P. E., 1912, Roy. Soc. Canada, Proc. and Trans., 3d sen, Vol. 5, 

 sec. 4, p. 117. 



