ANNIVERSARY ADDRESS OF THE PRESIDENT. 



Climacograptus confertus. Out of the entire fauna of the Arenig 

 Rhabdophora only 2 or 3 genera and species pass to the Llandeilo 

 rocks. 



Echinodermata. — No record whatever of this class in the Arenig 

 rocks. 



Annelida. — The whole group, of which 9 genera and 11 species 

 are described, possesses no zoological value ; they are simply worm- 

 burrows, worm-tracks, or trails of Mollusca. Ten of the 11 so-called 

 Annelide species occur in the Skiddaw Slates, the one unrepresented 

 form being Buthotrephis from St. David's. Scolithus linearis and 

 Helmintholitlies are in the Stiperstone beds also. No species has 

 occurred in North Wales ; and no species pass up from the Tremadoc 

 and Lingula-flags below. 



Crustacea. — The Arenig rocks have unequally distributed through 

 them 14 genera of Trilobites and 48 species, Ostracoda 2 (Beyrichia 

 and Primitiri) and the Phyllopod Caryocaris Wrighti increasing 

 the Crustacean fauna to 17 genera and 51 species. The special 

 Trilobita, however, number 41 species (6 coming up from the 

 Tremadoc and 2 passing to the Llandeilo, namely Trinucleus 

 Ramsayi and Homalonotus bisulcatus). No group in any of the 

 British rocks is so specialized as the Arenig Crustacea. The 

 Skiddaw rocks hold 9 species, representing 7 genera *; the Shelve 

 Arenigs have 10 species and 7 generaf, both areas showing either 

 imperfect collecting, or poverty in representation (which is by 

 no means likely). The few species (mostly single) known or 

 occurring in each genus clearly shows how large a fauna may 

 be expected if the more fossiliferous beds could be found in these 

 somewhat barren rocks. This applies equally to North "Wales, 

 where 9 genera are only represented by 11 species. In South 

 Wales (St. David's) the three areas have yielded 15 genera and 

 35 species. Circumstances have favoured collecting in this re- 

 gion ; and the known fauna is increased thereby. The Northern 

 or Skiddaw fauna is allied to the Shelve or Shropshire group through 

 3 species only (Agnostus Morei, Ogygia Selwynii, and JEglina 

 binodosa). The special Skiddaw forms are 4 only (Caryocaris 

 Wrightii, Phacops Nicholsoni, Niobe Doveri, and JEglina sp.) ; but 

 9 occur in these beds. The special Shelve species are Trinu- 

 cleus Murchisoni, Illaznus perovalis, I. Thomsoni, and Cheirurus 

 sp. ; but 10 species occur in the Shelve beds. The special North- 

 Wales species are also only 2, Asaphus affinis and Caryocaris Marrii. 

 The special South- Wales species are Agnostus hirundo, Asaphus 

 Homfrayi, Ogygia scutatrix, O.peltata, 0. bullina, Asaphus menapice, 

 Trinucleus JSedgwickii, Ampyx Salteri, yEglina boia, 2E. grandis, 2E. 

 obtusicaudata, Barrandia Homfrayi, Calymene ultima, and C. vexata ; 

 the occurrences in South Wales, however, are 35 species in 15 



* Caryocaris Wrightii, Agnostus Morei, Ogygia Selwynii, Trinucleus Gibbsii, 

 Mglina caliginosa, Salt., M. binodosa, JE. sp., Phacops Nicholsoni, and Niobe 

 Doveri. 



t Agnostus Morei, Oyi/gia Selwynii, Trinucleus Murchisoni, Mglina binodosa, 

 Calymene parvifrons aud var. Murchisoni, Illcsnus perovalis, I. Thomsoni, Chei- 

 rurus Frederici, and C. pectinatus. 



