212 TRANSACTIONS OF THE [May 18, 
Parvifrontes. ‘This group is distinguished by the incom- 
plete development of the glabella, which is not divided into 
lobes.” 
In eastern America this group appears first with the Abenacus 
sub-fauna, and has the following species : 
Agnostus parvifrons. 
SS vat besselia: 
A ———___ —_____—__ var. truncatus. 
A ——— umbo. 
Levigati. “ This group is distinguished by the more or less 
complete effacement of the glabella and the rachis of the pygi- 
dium.* The test is always smooth and shining, sometimes with 
traces of furrows. The marginal fold has a tendency to disap- 
pear from the head shield, but becomes broad on the pygidium.” — 
The group has been found in the Paradoxides beds of America, 
chiefly in those of Newfoundland. It comes in freely with the 
Davidis sub-fauna. 
The following species occur : 
Agnostus lavigatus, Dalm., var. terranovicus n. var. 
A var. ciceroides n. var. 
Ages var. mammilla n. var. 
CA nudus Beyr. 
In describing the following species the author has not followed 
Tullberg’s arrangement entirely, because he has found Longi- 
frontes rare in the first sub-fauna, their great development was 
in the third, fourth and fifth sub-faunas. On the other hand, 
the Regii appear to have been verging towards extinction, as in 
America they disappear with the advent of the Abenacus (third) 
sub-fauna. The arrangement adopted is Regii, Fallaces, Brevi- 
frontes, Longifrontes, Leevigati. 
The Agnosti of the American Paradoxides beds have a definite 
order of succession, corresponding nearly to that observed in 
those of Europe, viz.: 
In the P. lamellutus sub-zone are the following: Regii. A. 
regulus—fallaces. <A. fallax,and var. vir.,and var. trilobatus— 
Longifrontes. A. gibbus and var. partitus. 
In the P. Eteminicus sub-zone.—Vfallaces. <A. fallax and A. 
Acadicus. 
In the P. Abenacus sub-zone.—Regii. A. rex var. transectus 
—Fallaces. A fallax var. concinnus. A. Acadicus var. de- 
clivis—Parvifrontes. A. parvifrons and var. tessella and var. 
truncatus and A. umbo—JLongifrontes. A. obtusilobus. A. 
gibbus var. acutilobus, A. Natborsti and var. confluens, A. 
fissus and var. 3-fissus. 
*This last (the effacement of the rachis) is not a constant feature. 
