488 
SILURIAN TRILOBITES, 
that Phacops possessed the three ordinary pairs of glabella 
furrows, whilst Salter viewed the first pair as consisting of two 
parts, a feature in which Schmidt seems to agree with him, i.e., 
Salter's first pair is equal to Barrande's first and second. The 
arguments for and against the respective views of these authors 
are too long to be introduced here, but looking at the matter 
dispassionately there appear to be good grounds for supporting 
the opinions of Salter and Schmidt. 
The presence of the intercalary ring we regard as of very 
considerable importance in the limitation of Phacops proper. It 
is the "linear lobe" of Salter,* and the groove separating the 
ring from the glabella proper is the " maxillary furrow " of 
McCoy f. The intercalary ring is, in fact, formed by the con- 
fluence of the third pair of glabella furrows, with small circum- 
scribed lobes at the outer ends. It appears to mark off a series 
of species, including Phacops latifrons, Bronn, the type of the 
genus, P. cephalotes, Corda, P. fea.in.dus, Barr., and some others, 
from the remaining sections, sub-genera, or genera, whichever the 
reader prefers to regard them, usually associated under the 
broader name of Phacops of older writers. We therefore adopt 
Phacops as limited and defined more especially by Salter, and 
followed in many particulars by Schmidt. This restriction also 
has the advantage of comprising within it Emmrich's type of his 
genus, P. latifrons, Bronn. 
As regards species, we have succeeded in establishing the 
presence of three in the Silurian rocks of N~.S. Wales, viz. : — 
Phacops Crossleii, nobis. 
,, latigenalis, nobis. 
,, serratus, Foerste. 
And two in Victoria, viz. : — 
Phacops Sweeti, nobis. (? P.fecundus McCoy, non Barr.) 
,, mansjieldensis, nobis. 
If, however, P. fecundus, McCoy, be distinct from our P. 
Sweeti, then three forms are known from Victoria. 
* Mon. Brit. Sil. Trilobites, Pt. 1, p. 21. 
t Prod. Peal. Vict. 1876, Dec. iii. p. 15. 
