. A catalogue of the collection of Cambrian and Silurian fossils contained in the Geological Museum of the University of Cambridge. Paleontology; Paleontology. PI. 1H, f. 20—24, p. 229. p. Namos and References; Observations, &o. Siphonotreta micula, McCoy (Davidson, Mon. Sil. Brach. pi. 8, figs. 2—6). A pretty small Bracbiopod, covered with spines, and very nearly allied to the Discince. Larger spe- cies, with thicker shells, occur in the Lower Bala rocks of Russia and Sweden. Also in the Upper Silurian of Britain. Orthis biforata, Schlotheim: a variety with fine ribs. This common sp
. A catalogue of the collection of Cambrian and Silurian fossils contained in the Geological Museum of the University of Cambridge. Paleontology; Paleontology. PI. 1H, f. 20—24, p. 229. p. Namos and References; Observations, &o. Siphonotreta micula, McCoy (Davidson, Mon. Sil. Brach. pi. 8, figs. 2—6). A pretty small Bracbiopod, covered with spines, and very nearly allied to the Discince. Larger spe- cies, with thicker shells, occur in the Lower Bala rocks of Russia and Sweden. Also in the Upper Silurian of Britain. Orthis biforata, Schlotheim: a variety with fine ribs. This common species occurs over all the northern hemisphere. Orthis elegantula, var. parva, Pander. A va- riety only of the commonest of all British species of Orthis. It is comparatively rare in Lower Bala. [Orthis striatula, Emmons (Mem. Geol. Surv. Vol. in. pi. 13, figs. 10—14)]. Orthis calligramma, Dalm. (Mem. Geol. Surv. Vol. III. pi. 22, fig. 1). This common shell ranges from Russia to Britain; and from the Arenig to the Wenlock rocks. Orthis turgida, McCoy. A species with a remarkably tumid upper valve. Orthis confinis, Salter (Quart. Jour. Geol. Soc. v. , fig. 4, Davidson, 1. c. pi. 36, figs. 1—4). A large transverse species, with fine ribs. Is 0. sagittifera the same species ? Numbers and Localities. Strophomena. Rafinesque, Davidson, Salter. Differs from Orthis by having a widely expanded thin shell, and the cardinal pro- cess double. Strophomena concentrica, Portlock, Geol. Rep. p. 452. A shell extremely common in the Caradoc or Middle Bala rocks. Strophomena, sp. (S. expansa, McCoy in part). A very flat species, with a much thinner shell than Sowerby's Stroph. (Orthis) ex- pansa. The latter is a Middle Bala sp.— this is a common Lower Bala one. a. 102, Pen Cerrig, and Wellfield, near Builth, Radnorshire. a. 100, Tregib, Llandeilo. Rare in Lower Bala. Nant-yr-Arian, Llandeilo. Common in Lower Bala. Tan-y-graig, Builth (in vol- canic grit), a. 98, Cerrig Cregyn, Angles
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