BY R. ETHER1DGE, JUNR., AND JOHN MITCHELL. 497 
faint; side lobes tumid, seven or eight pleurae on each; pleural 
grooves very distinct anteriorly; sutures and axial grooves distinct. 
Obs. — This species was described by Foerste from a specimen 
sent to him by one of us. That specimen was distorted so that 
the true features of the head were indiscernible, particularly those 
of the eyes. In fixing the maximum number of lenses in the 
vertical rows at nine he is in error, for in a number of eyes 
examined by us the lenses in a row do not exceed five. By fore 
and aft compression it is not unusual to find an eye with two rows 
brought into the same vertical line, and in this way appearing to 
have nine or ten lenses in a vertical row. This is probably the 
case with Foerste's tj'pe specimen. 
We are inclined to agree with Foerste in ranking this as a species, 
for certainly it is very clearly separated from P. fecundus, Barr., 
by the greater inflation of the front of the glabella, the much 
smaller eye, the less distinct groove passing under the front of the 
glabella, the absence of granulation on the thorax, thinner test, 
straighter sides of glabella, greater perpendicularity of the sides 
of the thorax, greater distinctness of the pleural grooves on the 
pygidium, smaller size of the animal, and above all the presence 
of the very conspicuous dorsal spines. This latter feature 
separates it from all species of the genus known to us. 
From P. Crossleii, nobis, it is not separable except by the dorsal 
spines, and it may be that this feature is a sexual one, and the 
two forms represent the male and female of the one species. In 
a comparison of a number of heads of the two forms those of 
P. serratus, Foerste, seem to be more tumid in front and to have 
the glabella more sharply contracted behind by the intercalary 
groove. 
Log. mid Horizon. — Near Railway Station, Bowning, N.S.W. 
Upper Trilobite Bed, Bowning Series — A Wenlock. Coll. — 
Mitchell 
Phacops Sweeti, sp.nov. 
(PL xxxviii., fig. 9; PI. xxxix., figs. 1, 2; PI. XL., fig. 10.) 
[Compare Phacops (Odontochile) fecundus, McCoy (? non Barr.), 
Prod. Pal. Yict. 1876, Dec. iii. p. 15, t. 22, f. 8-9, t. 23, f. 1-6.] 
