PLEUROTOMARIA. 435 



flexuous radii in the base, so characteristic of the species, are lost, and only growth- 

 lines remain. Aperture subcircular. 



[Note as to the figures on Plate XXXVIII. — Figs. 1 a, 1 b, represent two aspects 

 of the early adult stage, where strong traces of the actinoniphaloid character still 

 remain. Fig. 2 represents three aspects of the early stage of one of the more rugose 

 forms. Specimens of this size and character are very common in the Goncavus -bed at 

 Bradford Abbas, though showing much variety amongst themselves. Fig. 3 repre- 

 sents two aspects of the early stage of a smooth variety, where the staircase-like 

 character of the umbilicus is preserved, but the umbilical rays are almost wanting. 

 Figs. 4 a, 4 b, represent the last stage of PI. actinomphala-abbas, where the actinom- 

 phaloid character is entirely lost, and the shell is smooth alike from age and wear. 

 Of these forms, too, there is a very great variety. Most of them exhibit a ten- 

 dency to gibbosity in the penultimate whorl ; there is also considerable variety in 

 the degree of depression, and in some instances the whorls of these old shells are 

 so much undercut as to produce quite a different figure.] 



All the above are from the Goncavus-hed, Bradford Abbas. In the Murchisonae- 

 zone of that locality are specimens which one hardly knows whether to refer to 

 PI. actinomphala, PI. Aglaia, or PI. Baugieri. 



376. Pleueotomaria Baugieri, d'Orbigny, 1850. Plate XXXIX, figs. 4a, 4b, 4 c ; 



and var., figs. 5 a, 5 b, 5 c. 



1850. Pleueotomaeia Baugiebi, d'Orbigny. Prod., i, p. 267. 

 1854. — — Terr. Jur., vol. ii, p. 463, pi. 



ccclxxviii, figs. 2 — 4. 



Description. — Though not attaining to so large a size, the English specimens 

 correspond satisfactorily with those described by d'Orbigny. 



Height (average) . . . .10 mm. 



Basal diameter . . . .28 mm. 



Shell subdiscoidal, largely umbilicate. The spire is coiled almost in the same 

 plane, and is composed of whorls which are subangular and in shallow gradations. 

 The whorls are spirally striated, and provided near the upper margin with a furrow, 

 the remainder of the space being radially ornamented with about twenty costse 

 having tubercular terminations. 



The sinus-band is placed near the outer margin in the furrow, wide, slightly 

 sunken, and flanked by raised lines. The body-whorl is subdiscoidal and bluntly 

 biangular ; the upper carina is formed by the nodular terminations of the 

 radial ornaments ; the lower, or peripheral carina, is also strongly nodular and 



