ANNIVERSARY ADDRESS OE THE PRESIDENT. 



163 



sented by 5 genera, 3 of which commence or first appear in this 

 division of the Upper Silurian strata. No less than 12 species of 

 Primitia, besides other Ostracods, have been determined by Prof. 

 Rupert Jones, F.R.S., two of them being Woolhope (Cyiliere Grin- 

 drodiana and Primitia lenticular is). Of the whole group of Crus- 

 tacea, 13 genera and 18 species pass up to the Lower Ludlow, whose 

 Crustacean fauna numbers 18 genera and 47 species. 



Bryozoa. — Of the 11 known genera that occur, 6 are new in 

 the Wenlock. JSTo less than 24 species are known in the shales 

 and limestones ; none have occurred in the Tarannon Shales, Den- 

 bighshire Grits, or anywhere in North Wales or Scotland. In South 

 Wales 2 species are known, Diastopora consimilis, Lonsd., and Ptilo- 

 dictya lanceolata ; the same species occur in Ireland, and, with Esclia- 

 rina angularis, Lonsd., pass to the Lower Ludlow. Fenestella 

 assimilis, F. suhantiqua, and Ptilodictya lanceolata were also Lower 

 Llandovery species. The 6 genera not known in the older rocks, 

 and which first appear in the Wenlock, are Cellepora, Geriopora, 

 Diastopora, Discopora, Escharina, and Polypora. 



Most of the Palaeozoic genera belong to the order Gynmolsemata, 

 suborder Cyclostomata. We know of no Palaeozoic genera extending 

 into the Secondary Period, where this class attains its maximum 

 paleeontological development, the Cretaceous system alone having 

 yielded more than 200 species. 



Brachiopoda. — In the Wenlock rocks, like the Caradoc, the Bra- 

 chiopoda greatly predominate over most of the other groups. We 

 have determined 15 genera and 109 species in the Caradoc ; and now 

 in the Wenlock are enabled to show that 22 genera and 101 species 

 occur, being an increase of 7 new genera (namely, Athyris, Cyrtia, 

 Eichwalclia,Nucleospira, Obolus,Orbiculoiclea, and Retzia), the species 

 being fewer so far as we know through the literature of the class. 

 21 genera and 96 of the 101 species belong to the Upper Wenlock 

 or Wenlock Limestone and shale*; all the known 22 genera are 

 also represented in the same horizon. The Woolhope beds yield 17 

 genera and 56 species, every Woolhope shell being also Wenlock. 

 Orthis mullochensis, Dav., or its variety O. reversa, may stand alone 

 as a Woolhope species, but every other form is equally Wenlock. 

 Certain horizons in the Wenlock rocks are richer generically and 

 poorer in species than others ; this is shown in the Tarannon Shales 

 and Denbighshire Grits, where, in the former, 10 genera occur 

 with only 15 species : it is the same with the Denbighshire Grits, 

 in which we have 14 genera and only 19 species. No genus or 

 species is peculiar to either the Tarannon or Denbighshire beds ; 

 all are good Upper Wenlock forms. Those species having the 

 longest range in time in the Wenlock group number about 11 ; they 

 also have a correspondingly wide range in space ; they are : — 



* The researches of Mr. Davidson, F.E.S., upon the collection made by 

 Mr. Gr. Maw in these beds has enabled him to add many new species and one 

 or two new genera to the fauna of the Wenlock rocks. 



