ANNIVERSARY" ADDRESS OF THE PRESIDENT. 



63 



primceva. Hicks, Distinct, sp., J), caerfaiensis, Hicks, and Leperditia 

 cambrensis, Hicks : these all occur in the lowest red shales below the 

 sands at Castell, on the east side of Ramsey Sound. About 1000 feet 

 of unfossiliferous red and purple grits and sandstones succeed this 

 first known fossiliferous group ; then, in yellowish-grey flaggy 

 sandstones, between Forth- Clais Harbour and Caerbuddy, we meet, 

 for the first time, with the gigantic Crustacea (Trilobita) Plutonia 

 and Paradoxides, and associated with them two genera, Microdiscus 

 and Agnostus, almost microscopic in size, and at the same time, or 

 in the same beds, Protozoa belonging to two species of Hexacti- 

 nellid sponges, Protospongia fenestrata, Salt., and P. major, Hicks, 

 and also two species of Pteropoda, Tlieca antiqua, Hicks, and T. 

 penidtima, Salt. I particularly mention this first assemblage of 

 life, as being, so far as I know, the earliest in the earitis history 

 on record ; and it consists nevertheless of forms whose organiza- 

 tion was not embryonic ; thus distinctly pointing to a line of an- 

 cestors belonging to this or some other area yet to be determined. 

 The entire fauna of these Pluto nia-heds consists of 8 genera and 

 9 species, 5 of which are Trilobita (viz. Plutonia Segiuickii, Hicks, 

 Paradoxides Harknessii, Hicks, Conocoryphe Lydellii, Hicks, Micro- 

 discus sculptus, Hicks, Agnostus cambrensis, Hicks), two Protozoa 

 (Protospongia fenestrata, Salt., and P. major, Hicks), with Lingulella 

 ferruginea, Salt., and Tlieca antiqua, Hicks ; three of these, Para- 

 doxides Harknessii, Agnostus cambrensis, and Protospongia fenestrata, 

 pass to the Menevian group. Plutonia Sedgtvichii, Conocoryphe 

 Lyellii, and Microdiscus sculptus have not been detected in any 

 higher horizon, and P. Harknessii only in the succeeding red, 

 grey, and purple flaggy sandstones, where it is associated with 

 Conocoryplie solvensis, which represents Conocoryphe Lyellii below. 

 Grey and purple sandstones, 1500 feet thick, but with a scanty 

 fauna of only five species, including the doubtful Eophyton, succeed 

 the PZ^om«-sandstones. Finally the Harlech and Llanberris group 

 at St. David's terminates with grey flaggy sandstones, which contain 

 another form of Paradoxides (P. aurora), Conocoryplie bufo, Hicks, 

 and Agnostus cambrensis, Hicks; in all eight species are known to 

 occur. 



This first incoming of life in the British rocks and in the SL- 

 ID avid's area exhibits a singular assemblage and grouping of 

 species, doubtless owing to our limited acquaintance with' the then 

 existing fauna, rendered obscure through the present state of our 

 collections. Numerically the fauna of the Lower Cambrian com- 

 prises 61 genera and 182 species, ranging from the lowest red 

 shales of the Longmynd group to the top of the Tremadoc. The 

 Longmynd and Harlech beds yield 18 genera and 32 species, the 

 Menevian group of South Wales 24 genera and 51 species, the 

 Lower Lingula-flags of all localities 17 genera and 36 species, the 

 Upper Lingula-flags 14 genera and 41 species, the Lower Tremadoc 

 29 genera and 59 species, and the Upper Tremadoc 20 genera and 

 33 species. Of this Lower-Cambrian fauna (61 genera and 182 

 species) only 9 genera and 12 species pass to the Arenig ; of these, 



