40 BRITISH OOLITIC AND LIASIC BRACHIOPODA. 



Diagnosis. Shell obovate, transverse, valves nearly equally convex, gibbous, beak more 

 or less recurved and rounded, foramen entire, with lateral ridges recurved and joining the 

 hinge margin within a short distance of the beak; deltidium in two pieces, more or 

 less visible, according as the beak becomes more or less recurved : front straight or slightly 

 convex, bounded by two obsolete plaits, sides rounded, margin rather flat, loop simply 

 attached to the Crura and extending to near the front margin. Dimensions variable, length 

 15, width 13, depth 10 lines. 



Obs. This species was correctly described by Sowerby in 1812. It is a thick globose 

 shell, abundantly spread in the Cornbrash of many localities ; as at Rushden, in 

 Northamptonshire, where it attains large dimensions, as may be seen from a suit of 

 specimens from that locality, presented to the British Museum by Mr. Waterhouse. It is 

 also abundant in Wiltshire, where specimens showing the loop to great perfection can be 

 obtained. It occurs near Scarborough, where it was obtained by Mr. Bean, and is likewise 

 found in many parts of the Continent; at Boulogne, by Mr. Bouchard. D. Bronn does 

 not appear to have been acquainted with this species, from what we find in the 'Index 

 Palaeontologicus.' It is always more globose than T. digona, and does not present any frontal 

 angles, its greatest width is also considerably increased towards the middle of its length. 

 PI. V, fig. 16, illustrates one of the original specimens of the M. C. 



„ 14, 15, two full-grown specimens from the British Museum ; fig. 17 showing 

 a curious deformity in this species, in which the accident is reproduced 

 on both valves. 

 PI. VII, fig. 5, is a very curious shell found in the Cornbrash of Norman Cross, by 

 Mr. Morris, along with the true types of obovata and lagenalis ; after 

 minute comparisons, Mr. Morris and myself came to the conclusion that 

 it can only be a deformity of the species under consideration. 



35. Terebratula ornithocephala, Sow. Plate VII, figs. 6, 13, and 23. 



Terebratula ornithocephala, Sow. 1812. Min. Con., vol. i, p. 227, tab. 101, 



figs. 2, 3, 4. 



— lampas, Sow. 1812. Min. Con., vol. i, p. 228. 



— triquetra, Sow. 1825. Min. Con., vol. v, p. 65, tab. 445, fig. 1. 



— ornithocephala, Smith. 1816, 1817. Stratigrapbical System of 



Organised Fossils. 



— — Desk. 1836. Nouv. Ed. de Lamarck, vol. vii, p. 361. 

 _ _ Phillips. 1836. Geol. of Yorksh., vol. i, tab. 6, fig. 7. 



— — Zieten. 1832. Die vers. W'urt., tab. xxxix, fig. 2. 



— — Morris. 1843. Catalogue of British Fossils. 

 — Bronn. 1849. Index Palaeont., p. 1243. 



_ _ D'Orb. 1849. Prodrome, vol. i, p. 316. 



— SCBTRIOUETRA, D'Orb. 1849. Prodrome, vol. i, p. 216. 



