76 ROYAL SOCIETY OF CANADA 



Strenl'ELLa strenl'a, Billings sp. 



1874, Agi-aulos strtnuiis. Hill., Pala-o/oic Foss., vol. ii., pt. 1, p. 71, lig. II. 



1886, A. strenmwi, Bill., Ciiinbr. Faunas of C. Breton and Newfoundland, Trans. Roy. 



Soc. Can., vol. iv., pt. iv., p. 103, flgs. .'i, 3a and b. 

 1888, Ptychopuria mwcro««<a, Shaler and Foreste (pars) Bull. Mus. Conip. Zoo!, vol. 



xvi.. No. 2, p. 37, pi. 2, fig. 216. 

 1800, Ayrnulos st remues (Bill.), Wale, Fauna of Olencllus Zone, p. Ciô^i, \)\. xcvii., 



flgs. 1, l/>, and c. 



The description of this species as given by BiUings is quoted by the 

 author in Transactions of the Royal Society of Canada. Walcott refera to 

 this species the Ptychopan'a mucronata of Shaler and Foerste, with which 

 the author agrees as regards one of the figures given by these authors — 

 the larger figure (216), the smaller one (21a) is probably a larval head. 

 Of the forms figured by ^Ir. Walcott in the work above cited, figs. 1, \b 

 and c, appear to belong to this species and la probably to the following 

 mutation. 



nnit KOBUSTA n, rant. (PI. IV.. fig, 3.) 



Ayraulos strenuus, var. Trans., Roy. Soc. Can., vol. iv., pt. iv., p. 154. 

 cf. A. strenuus (3i\l.), Wale, Olenellus Zone, pi. xcvii., lig. la. 



Only the middle piece of the head is known. This is sub-trapezoidal 

 and is strongly arched in front. The anterior marginal fold is broad, flat 

 and strongly curved in front ; it is separated from the glabella by a 

 narrow, but distinct furrow. The glabella is cylindro-conical and quite 

 prominent ; it is a quarter narrower at the front of the eye-lobes than at 

 the occipital ring, and is evenly rounded in front ; it is separated from the 

 ring by a shallow furrow extending all across, but most deeply impressed 

 in the outer third. The glabella shows one pair of furrows, faintly im- 

 pressed at the side ; but the mould of the head-shield shows two pairs of 

 furrows, turned backward, and a very faint, third pair, turned forward. 

 The occipital ring is broad and has a short spine projecting backward. 



The fixed cheeks were narrow ; exclusive of the eye-lobe the cheek 

 was half of the width of the glabella, and is depressed before and behind. 

 The ocular fillet which is low, begins in a low tubercle near the glabella. 

 The pali)ebral lobe was wide and long ; it was half as wide as the cheek 

 and as long as the width of the cheek and eye-lobe together. The pos- 

 terior marginal fold widens rapidly toward the suture, and is strongly 

 geniculate at the middle, whence the posterior margin of the shield 

 advances forward rapidly toward the dorsal suture. The suture extends 

 directly backward from the eye-lobe to the posterior margin, and directly 

 forward in front of the eyes. 



Sculpture. — The surfiace of the test is minutely granulated. 



