Dr. H. Woodward—Bronteus from Devonian, Eifel. 409 
margin, where they terminate in short flattened strong marginal spines. 
The interspaces between the ribs form smooth sulci, narrow at the 
anterior end, where they diverge from the axis, and broader near the 
flattened margin, where they gradually die out. 
The shelly cuticle or crust of the pygidium has been lost along 
about three-fourths of its expanded margin, exposing the cast of the 
under surface of the caudal shield, which was covered by a series of 
fine, wavy, more or less parallel lines, as may also be seen upon the 
decorticated surface of the pygidium in Jd/enus, Ogygia, Asaphus, and 
some other genera. 
In the genus Bronteus the coalesced segments forming the pygidium 
are usually seven in number, but two species are recorded by Barrande 
with only six, viz. B. laticauda, Wahl., and B. hibernica, Portl., while 
one species, 6. radiatus, Munst., is said to have eight ribs in the 
tail-shield. The prolongation of the axis forming the median ridge 
to the pygidium is most commonly bifurcated! at or near the distal end. 
With very few exceptions the margin of the pygidium in the several 
species of Bronteus is smooth and destitute of spines or spinous 
prolongations along its border. 
Mr. Townshend Hall’s specimen (Fig. 1) has fifteen spines around 
the tail-shield, marking the terminations of the pleurs of the seven 
coalesced segments which compose it, the fifteenth median spine being 
a prolongation of the distal end of the axis. 
4 
Fic. 2. Bronteus thysanopeltis, Barr. Upper Silurian: Bohemia. The median 
ridge of the tail does not appear to be bifurcated ; it has forty-five 
marginal spines on the pygidium. 
, 8. Id. A detached pygidium, having thirty-three spines along its, border. 
This figure has the median ridge of the tail-shield bifurcated. 
» 4. B. speciosus, Corda. Lower Middle Devonian. With forty marginal spines 
to its pygidium. ‘This species has the median ridge bifurcated. 
1 Thirty-one species being bifurcate, and nineteen non-bifurcate. 
