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BULLETIN OF THE NATURAL HISTORY SOCIETY. 
The reticulation of raised lines is more distinct on the interior than 
on the exterior surface of the test. A similar but faint reticulation is 
visible on the front half of the fixed cheek. The surface of the glabella, 
seeming smooth, when viewed with a lens appeals to be faintly- 
marked with scattered pits or depressions. The front and lateral 
marginal fold of the head-shield, when viewed with a strong lens, is 
seen to be minutely striate lengthwise of the fold. 
Size. — The head-shield figured is not the full size of this species, 
for some pleune shows that it grows to a size one-quarter longer. 
This species is closely allied to P. acanthura , Ang from which it 
differs in the following respects : The area in front of the glabella is 
wider and more strongly arched, and the fixed cheek is more pointed 
at the posterior outer angle. In the free cheek the rim is more strongly 
arched in front, and has less width behind. The joints of the 
thorax have tubercles, or, in some cases, spines on the rings. The 
pygidium has a median tubercle on each cf the first two joints, and 
the marginal spines of which only one pair is known, are directed out- 
ward rather than backward. In other respects the two species, in so 
far as comparisons can be made with the imperfect material obtained j 
are much alike. 
This species is distinguished from Protopeltura acanthura , var. 
tetracanthura,j by the broad area in front of the glabella, and by its 
broader pygidium with fewer joints. From Parabolina heres, var. lata, l 
it differs in the arched anterior border fold, and narrow fixed cheek. 
From P. heres, as depicted by Brogger, it differs in its shorter pygid- 
ium of fewer joints ft From P. acanthura, as figured by the same 
author, in its more quadrate glabella, and in the tubercles on the rings 
of the rachis of the pygidium. }J From P. heres, as shown by Moberg 
and Moller, in the absence of strong reticulation on the surface of the 
fixed cheek, and the fewer joints in the pygidium. § From P. 
acanthura, as figured by these authors, in the arched front of the head- 
shield, and in the presence of tubercles on the rachis of the pygidium. || 
* Palseontol. Scand., p. 49, pi. xxvi, fig. 9. Also Om Acerocare, Moberg & Moller, Stock, 
holm, 1898, p. 2.9, tafl, 12, figs la and 4a. 
+ Roy, Soc. Can , Tians., vol. ix, sec. iv, p. 53, pi. xiii, figs. 8a-c. 
X Roy, Soc. Can , Trans,, vol ix, p. 5 1 . pi. xiii, figs 6a-/. 
if Dii Silurish. Etag. 2 und 3, p. 101, tab. i, fig. 13d. 
XX Idem, p. 106, tab. 14, 14c. 
§ Om. Acerocarezonen, Stockholm, 1898, p. 267, tafl. 12, figs. 8a, 11a. 
I Idem, p. 259, tafl 12 figs, la and 4a. 
