176 ROYAL SOCIETY OF CANADA 



also is proportionately more slender ; otherwise the three posterioi^ 

 segments and the pygidium are almost identical with those of the type. 



Size. — Length of the head, 35 mm. ; width of the middle piece of 

 the head at the front and back, 47 mm. ; at the eyelobes, about 44 mm. 



Horizon, as noted above. 



This form differs from P. Bohémiens, P. Tessini and P. Davidis in 

 that the last pair of pleurœ are weaker than the others. 



AGEAULOS, Corda. 



Agraulos ceticephalus, Barr., var. carinatus, n. var. (PI. II., 



Figs. 2a and 6.) 



Arionellus ceticephalus, Barr., Faune Primordiale dans la chaine Cantabrique, 

 p. 526, pi. vi., figs. 13 to 17. 



A head shield, which by its size and general form, appears to belong 

 to Barrande's species cited above, occurs sparingly in this sub-fauna, but 

 it differs to some exient from the European form. 



The glabella is more simken, but though the dorsal furrow is faint, 

 the prints of the glabella furrows are distinct, and the occipital furrow 

 does not cross the axis of the shield. The back of the occipital ring is 

 broken away, but there probably was a spine. There is a marked ridge 

 which traverses the head-shield on the axial line, except on the low, 

 narrow, anterior marginal fold. 



A young head of the form of this species has an occipital spine 

 nearly as long as the glabella ; the dorsal furrow is more distinctly 

 defined, and the anterior marginal furrow and the ocular fillet more 

 prominent. 



Sculpture. — The surface is minutely punctate. 



Size. — Length of the head-shield, except the spine, 10 mm. ; width 

 of the middle piece of the head at the front, 10 mm. ; at the eyelobes, 

 13 mm. ; at the back, 15 mm. 



Horizon. — In a limestone band of the gray shale. Scarce. 



Agraulos holocephalus, mihi. (PI. II., figs. 3a and b.) 



Agraulos holocephalus. Trans. Roy. Soc. Can., vol. viii., pt. iv., p. 188, pi. xi., 



figs. 5 a to d. 



This species was discovered some years ago in the black siliceous 

 shales. In most examples of the head the glabella is more distinctly out- 

 Imed than in the type, but in others it is quite as obscure ; the occipital 

 furrow is slightly marked at the sides of the glabella, in some examples 

 it does not cross the axis. It is a smaller species than A. ceticephalus ; but. 



