8ib YORKSHIRE TYPE AMMONITES— II August 



81. AMMONITES BRAIKENRIDGII, J. Sowerby 

 (Plate LXXXI) 



Original Description 

 [J. Sowerby. Min. Conch. Feb., 1818. II, p. 187.] 



" Ammonites Braikenridgii. 

 " Tab. clxxxiv. 



" Spec. Char. Depressed ; radiated ; volutions exposed ; front 

 rounded ; crossed by the radii ; radii furcate ; mouth round ; 

 lip expanded into two oblong lobes. 

 " Radii prominent, numerous, rather sharp, and equal to the spaces 

 between them : there is a small tubercle upon each at the base of the 

 branches ; the thickness of the last whorl is rather less than one-third 

 the diameter of the shell : there are about three or four volutions. The 

 lip is very striking, it commences with a square base, and having been 

 continued a little way from the last radius it suddenly expands on the 

 sides into two oblong lobes, on which are distinctly marked the lines of 

 growth : the edges are sharp, and gradually bent a little inwards. 



" Perfect terminations of the Ammonites are rare ; I have, however, 

 met with several specimens indicating the form of the lip, but none 

 of them exhibit anything much out of the usual way, excepting some 

 French ones, and those now before us : in one of the French specimens 

 the aperture is much contracted by the lip ; in another, the lip forms 

 a single arched lobe slightly bent inwards.* 



" These remarkable fossils are from Dun dry near Bristol : they 

 are composed of foliated carbonate of lime, and are embedded in a 

 compact limestone, replete with rounded shining grains of yellowish 

 brown oxide of iron, and the remains of various other shells. They 

 enrich the collection of George Weare Braikenridge, Esq. of Bristol. 



" * Of these I have made an engraving for comparison [Plate A] ; they are found in a 

 similar stone with the British one, at Bayeux in Normandy, and were presented to me by 

 Mons. de Gerville, to whom I am much indebted for the fossil produce of the Cotentin." 



Remarks 



Proportions : 44, 33, 37, 41 ; subplaty-, pachygyral, latum- 

 bilicate. 



Stages, conch, serpenticone ; periphery, 1 ; ornament 5. 



Ribs slightly prorsiradiate, sharp on side up to small tubercle, 

 where they bifurcate regularly, and are rounded : they pass straight 

 over a somewhat medianly flattened periphery. The auricle rises 

 sharply, is spatulate, has not a true lateral, but a somewhat latero- 

 penpheral position. The inner edge of auricle is about in line with 

 tubercles, and the auricle is thrown more peripherally by the rise from 

 whorl being sharp in inner part, but flush as it merges into periphery. 



Genus, Otoites, Mascke, 1907, 25 ; family Otoitidae, Mascke. The 

 species belongs to the Am. sauzei group (Otoites), and not to the group 

 of Am. braikenridgii] d'Orbigny, Normannites (see S. Buckman, 1908, 

 140). Its ears are somewhat more peripherally situated than is the case 

 in its allies, but they are not so peripheral as in Normannites. Further 

 it is distinguished by the peripheral ribs being rounded instead of 

 sharpened. It is, for an Otoites, a rather umbilicate species. 



