RHYNCHONELLA. 161 



this matter, he has unconsciously proved that Sp. aculeata, Schnur, is a synonym 

 of Spiriferina pulchella, Sowerby, sp. 



III. Family — Rhynchonellid^, d'Orbigny, 1847. 



1. Genus — Rhynchonella, Fischer de Waldheim, 1809. 



Sub-genus — Camarotcechia, Hall and Clarke, 1894. 



1. Rhynchonella (Camarotcechia) Partridgle, Whidborue. Plate XIX, figs. 12 — 14. 



1841. Terebratttla pleurodon ?, Phillips (pars). Pal. Foss. (uot Geol. Yorks.), 



p. 86, pi. xxxv, figs. 155 a, I. 

 1865. Rhynchonella pleurodon, Davidson (pars). Mori. Brit. Toss. Brach., 



vol. iii, p. 62, pi. xiii, figs. 12, 13. 

 1896. — Partridgii, Whidborne. Proc. Geol. Assoc, vol. xiv, 



p. 376. 



Description. — Shell generally rather small, transversely oval or sub-pentagonal, 

 apparently becoming more transverse with age. Ribs strong, elevated, acutely 

 triangular, reaching to the umbones, and deeply interlocking at the margins, sepa- 

 rated by furrows. Ventral valve with a rather elevated and erect sharp beak, and 

 a sinus which becomes deep in front, so that the " languette " forms a low sub- 

 tetrahedron. Ribs, three on the sinus and about seven on the sides. Lateral 

 ribs with a slightly concave sweep, and terminating marginally with a sharp angle. 

 Dental plates oblique, reaching about one-third down from the beak, their front 

 ends being joined by a low curved ridge which defines the muscular impressions. 

 Dorsal valve with a flat and straight median fold, becoming prominent in front 

 and sharply angulatecl at the margin, containing almost invariably four ribs. 

 Sides dilate and drooping. Median septum reaching nearly half-way to the front, 

 and having at its posterior end diverging branches which support the dental 

 sockets (?), which are crenulated exteriorly. 



Size. — Some specimens are more than 24 mm. wide. 



Localities. — Pilton Vicarage Well, Poleshill, Top Orchard, Roborough, 

 Goodleigh, Raleigh, Bradiford, Frankmarsh, Collar Bridge, Kingdon's Shirwell, 

 Saunton, Croyde Bay, Laticosta Cave, Ashford Strand, Upcott Arch Quarry, 

 Ashhill Quarry, Pouch Bridge, Fremington, &c. 



Remarks. — This species is abundant and wide-spread in the Pilton Beds, but 

 being usually crushed, contorted, or fragmentary, its exact characters are not easy 

 to define. In writing of it Phillips specially remarks on the difficulty of deciding, 



x 



