. A catalogue of the collection of Cambrian and Silurian fossils contained in the Geological Museum of the University of Cambridge. Paleontology; Paleontology. Barmouth Boad. Traeth bach. Portmadoc Estuary : shewing the relations of the Menevian (c), Ffestiniog (d), Tremadoc (e), and Arenig Groups (f) in the district around Portmadoc, N. Wales. By the Eev. A. Sedgwick, 1847, and J. W. Salter, 1853—7. The faults are all by J. W. S. The strata, in descending order, are:— f. Arenig (or Skiddaw) Group. Dark earthy slates on a base of sandstone ( = Stiper Stones, Shropshire). e. Tremadoc Grou
. A catalogue of the collection of Cambrian and Silurian fossils contained in the Geological Museum of the University of Cambridge. Paleontology; Paleontology. Barmouth Boad. Traeth bach. Portmadoc Estuary : shewing the relations of the Menevian (c), Ffestiniog (d), Tremadoc (e), and Arenig Groups (f) in the district around Portmadoc, N. Wales. By the Eev. A. Sedgwick, 1847, and J. W. Salter, 1853—7. The faults are all by J. W. S. The strata, in descending order, are:— f. Arenig (or Skiddaw) Group. Dark earthy slates on a base of sandstone ( = Stiper Stones, Shropshire). e. Tremadoc Group. Dark slates, iron stained, and with felspathic beds—1500 feet thick. d. Ffestiniog Group. Thick flaky sandstones, 2000 feet, and a bed of black slate 300 feet. c. Menevian Group. Dark slate and sandstone—only the top beds (with Olenvs cataractes). d. Ffestiniog Group Middle Upper Linsfiila flag. j Sandstones, hard, laminated, flinty, 2000 feet thick. I Black Slates, often stained with iron, 200 to 1000 feet. Case and Column of Drawers. Reference to McCoy's Synopsis: and Figures of Genera. Gh Graptolites. Horny sheaths, with a slen- der solid axis, and with nume- rous close-set cells opening into the common sheath. The mouths often armed with Names and References; Observations, &c. AM0RPH0Z0A. None yet known. P0LYZ0A or HYDR0ZQA? (Graptolitidce). Considered by Prof. McCoy and some other authors as Sertularian Zoophytes. I there- fore place them here in the order given to them in the Synopsis. (See for their affini- ties, Mem. Geol. Surv. Vol. III. p. 328, and Carruthers, Geol. Mag. Vol. V. pi. v.) Dictyonema (Graptopora) sociale, Salter (Mem. Geol. Surv. Vol. in. pi. 4, fig. 1). Vari- ously known as Gorgonia, Dictyonema, and Graptopora. A net-like fossil, allied to the Fenestella and Polypora of the Bala and Wenlock rocks: but of horny texture and with cells in double row, like Graptolites. (Salter, Mem. Geol. Surv. Vol. in. p. 331.) Numbers and Localitie
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