90 PROCEEDINGS OP THE GEOLOGICAL SOCIETY. 



North Wales until Prof. Hughes discovered portions of one in Angle- 

 sey. If any other Trilobite were required to establish palseontological 

 relationship between the Tremadoc rocks of North and South Wales 

 it would be Angelin a genus Niobe ; and Dr. Hicks has obtained, both 

 from Ramsey Island and Tremanhire, a new and splendid species 

 (Niobe menapiensis), greatly exceeding in size the characteristic 

 Niobe Homfrayi from Penmorfa and Tremadoc. Niobe is not 

 known out of the Tremadoc group. The South- Wales beds do not 

 possess so numerous an assemblage of pelagic Mollusca as those of 

 North Wales : 9 species of Pteropoda (Theca Davisii, T. 

 opercula, Lower Tremadoc only, T. arata, T. bijugosa, T. cuspi- 

 data, Lower and Upper, and T. alata, T. simplex, and T. tri- 

 lineata, with Conularia Homfrayi) are Upper Tremadoc; and 5 

 Heteropoda (Bellerophon arfonensis, B multistriatus, B. ramsey- 

 ensis, B. solvensis, and B. shinetonensis) range through the Trema- 

 docs ; but TJieea Davisii, Bellerophon ramseyensis, Hicks, and Bo 

 solvensis, Hicks, are South- Wales species, the mass occurring in the 

 typical Tremadoc area in North Wales. Associated with Niobe 

 menapiensis and the Neseureti no less than 19 species occur, 

 including the 12 Lamellibranchs and 5 Brachiopoda, viz. Lin- 

 gulella Davisii, Lingula petalon, Obolella plicata, Orthis Carausii, 

 and 0. menapice, 29 of the 31 being described by Hicks. 

 Dr. Hicks believes that the lower portion of the St.-David's 

 Tremadoc rocks and the upper black slates of the Lingula-flags of 

 North Wales were deposited contemporaneously. This may well be, 

 looking at the remarkable difference existing in the faunas of the 

 two areas, so few species being common to or uniting the two groups, 

 and difference of depth at the time of deposition. Again, the 

 absence of the fine black slates in the Upper Lingula-flags of St. 

 David's, so characteristic of the North-Wales and the Malvern beds, 

 may be due to depth, shallow in one region and deep in the other. 



The Tremadoc series is divided into three groups by Dr. Hicks, 

 the lowest at St. David's consisting of grey, fissile, or flaggy sand- 

 stones. Exposed at Ramsey Island, Tremanhire, and Llanveran, a 

 peculiar assemblage of fossils occurs in this area, new and different 

 from that of North Wales : — Davidia, Glyptarca, and Palmarca, 

 being the earliest bivalves known ; the earliest Crinoid, Dendrocrinus 

 (unless Mr. Callaway's genus Macrostella from the Shineton area 

 should be earlier in time) ; and the first known Asteroid, Palceasterina 

 ramseyensis, Hicks. The Middle Tremadoc of Hicks is equivalent to 

 the passage-beds between the Lower and Upper series of Salter, con- 

 taining Cheirurus Frederici, Conocoryplie verisimilis, C. vexata, and 

 Asaphus Homfrayi, — the upper member, consisting of iron-stained 

 slates and flags at Penclogwyn, Garth, Dudreath Tuhwnt-yr- 

 bwlch, &c, in the Portmadoc area being characterized by Angelina 

 SedgwicJcii, Lingulocaris lingulascomes, and Conularia Homfrayi. 

 The distinctness of the Tremadoc from the Lingula-flags below is in 

 all areas the same ; only 8 species out of 65 known forms in the 

 former pass up to the Tremadoc, which possesses a fauna of 84 

 species ; these are Agnostus prineeps, Ampyx prmnuntius, Conocoryplie 

 depressa, Lingulella Davisii, L. lepis, Orthis lenticularis, Obolella 



