BY R. ETIIKRIDGE, JUNR., AND JOHN iMITCHELL. 



We do not notice incidental references to other localities, when 

 unaccompanied by descriptions, nor catalogue names in the same 

 category. 



The Tasmanian forms are at present undescribed. 



The Phacopidce is represented throughout Australian Silurian 

 rocks, so far as we can ascertain with certainty, by two genera 

 only — Phacops, Emmrich, and Hausmannia, Hall and Clarke. 

 During our researches we have not met with any Trilobites that 

 could be referred to either of the following : — Acaste, Goldfuss; 

 Chasmops, McCoy; Pterygomietopiis, Schmidt; TrimeroQephalus, 

 McCoy; Portlockia, McCoy; CryphcBiis, Green; Coronura, Hall 

 and Clarke; Odontocephalus, Hall and Clarke; or Cori/cephalus, 

 Hall and Clarke. 



We imply a doubt because the subject of our PI. xxxix. tig. 12, 

 appears to foreshadow a third section or genus, but the material 

 is too scanty to enable us to pass a definite opinion. 



Genus Phacops, Emmrich, 1839. 



Phacops in its restricted sense, following the researches of 

 Salter^ and Schmidt,! and to some extent of Barrande| also, omit- 

 ting other minor characters, is distinguished from other members of 

 the Phacopidag chiefly by the presence of the two anterior pairs of 

 glabella furrows, generally linear in character, and of which the 

 first or anterior pair frequently consists of two branches. The 

 fore part of the glabella, formed by the frontal and lateral lobes, 

 is, as a whole, cut off from the neck segment by the intervention 

 of a supplementary ring, termed by Barrande the " intercalary 

 ring " (anneau intercalaire)§. Barrande used this feature as one 

 of the chief distinguishing points between the only two genera 

 recognised by him in the Bohemian Silurian rocks, Phacops and 

 Dahna7iia (vel Dalmanites). This eminent author considered 



* Mon. Brit. Sil. Trilobites, Pt. 1, pp. 13 and 14. 

 t Mem. Soc. Imp. Sci. St. Petersb. 1881, xxx. (7), No. 1. 

 X Syst. Sil. Boheme, 1852, i. p. 498. 

 § Loc. cit. p. 505. 



