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GASTEROPODA OF THE INFERIOR OOLITE. 



216. Amberleya Murchisoni, Miinster, 1844. Plate XXII, fig. 11. 



lSii. Tuebo Muechisoni, Munst. Goldf., Petref., pi. cxciv, fig. 10. 



Except that ours is a better specimen, showing the apical conditions, there 

 seems no difference between the fossil from the Humphriesianus-zone of Bradford 

 Abbas and the one figured by Goldfuss. No other British specimen is known to 

 me. Amb. Obornensis, next described, is probably only a variety. 



217. Ambbrleya Obornensis, sp. nov. Plate XXII, fig. 10. 



Description : 



Length ..... 25 — 35 mm. 

 Length of body-whorl to total height . . 48 : 100. 



.Spiral angle .... 40°. 



Shell eucycloid, turrited. Spire pointed, with an obtuse apex. Whorls nine 

 or ten, sutures very wide. The apical whorls smooth, full, and flattened towards 

 the summit (the enlargement of figs. 6 and 11 is also suitable for this species), 

 the succeeding whorls sub-biangulate, spirally ornamented, with the principal keel 

 almost median. Close to the suture is a posterior row of tubercles, which are 

 rather small and wide apart ; next succeeds the flat sloping area, with axial stria?, 

 also rather wide apart ; then the principal keel, which forms the angle of the 

 whorl, the tuberculations being of moderate size ; the lower median carina 

 has the tuberculations still smaller and numerous ; and below this, owing to the 

 gaping of the suture, an additional carina, corresponding to the first spiral in the 

 base, may frequently be detected. 



The body-whorl is angularly ventricose, the keel being situated rather high 

 up, so as to shorten the posterior area, which together with the rest of the shell 

 is axially striated, the strise being rather wide apart. 



The aperture is ovate-elongate, with a straight columellar lip produced 

 anteriorly, somewhat after the manner of Purpurina, with a tendency to become 

 more circular in the larger and more mature specimens. 



Relations and Distribution. — Amberleya Obornensis, which is at least a good 

 local variety of Amb. Murchisoni, although clearly a member of the goniata- 

 group, has certain affinities with the more elegant forms of Amb. ornata, var. 

 abbas. To a certain extent, then, it may be regarded as intermediate between 

 the ornata- and goniata-grou-ps, though its relations are mainly with the latter. 



This intermediate character corresponds with its stratigraphical position in 



