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.fecaudiis, 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 Crossltii, nobis. 

 ,, Iatige7ialis, nobis. 

 ,, serratus, Foerste. 

 And two in Victoria, viz. : — 



Phacops Sweeti, nobis. Q P. focundus McCoy, 7ion^&Tr.) 

 „ mansfieldensis, nobis. 

 If, however, P. fecundus, McCoy, be distinct from our P. 

 Stveeti, then three forms are known from Victoria. 



* Mon. Brit. Sil. Trilobites, Pt. 1, p. 21. 

 t Prod. Pal. Vict. 1876, Dec. iii. p. 15. 



