PHOLADOMYA. 249 
Affinities —By some authors this species has been identified with P. Martini, 
Forbes. With the material at present available it is difficult to make a satisfactory 
comparison ; but the specimens from Speeton are of considerably larger size, with 
broader and less prominent umbones, and with the posterior part of the shell less 
compressed than in P. Martini. 
In form this species resembles P. alternains, Rémer,! but the umbones are 
relatively higher, and the radial ribs more numerous. The ribs are not so numerous 
as in P. Hberti, Wollemann.’ 
Remarks.—The specimens from the clays are considerably crushed, whilst in 
those from the hard nodular beds a more or less considerable portion of the 
marginal part of the shell is missing. 
Distribution.—Speeton Clay (zones of Pelemnites lateralis, B. jaculum, and B. 
brunsvicensis) of Speeton. 
PaotapomyaA Martini, Forbes, 1845. Plate XLI, fig. 5. 
’ ’ 2 fo) 
1845. PHotapomya Marvint, H. Forbes. Quart. Journ. Geol. Soc., vol. i, p. 238, 
pl. u, fig. 3. 
1850. — os A. d’Orbigny. Prodr. de Pal., vol. 11, p. 117. 
1854. = — J. Morris. Cat. Brit. Foss., ed. 2, p. 220. 
1865. — _- F. J. Pictet and G. Campiche. Foss. Terr. Crét. Ste. 
Croix (Matér. Pal. Suisse, ser. 4), p. 92. 
? 1908. ~- A. Wollemann. Jahrb. d. k. preuss. geol. Landes- 
anst. fiir 1908, vol. xxix, p. 165, 
pl. x, fig, 3. 
Description.—Shell rather small, oval, very inequilateral, anterior part inflated, 
posterior part compressed. Umbones prominent. Escutcheon deep. Ornamenta- 
tion consists of numerous radial ribs, which are more or less tuberculate, and are 
more widely separated anteriorly than on the median part; on the anterior and 
postero-dorsal parts ribs are indistinct or absent. Concentric ribs and growth-lines 
are present. 
Remarks.—lt is difficult to give a satisfactory description of this species, since 
the specimens seen are few in number, imperfectly preserved, and usually crushed. 
P. Martini appears to be closely allied to P. Fabrina, VOrbigny (see below). It 
also resembles P. hispainica, Coquand.® 
1 Wollemann, ‘ Die Biv. u. Gastrop. d. deutsch. u. hollindisch. Neocoms’ (1900), p. 134, pl. v, figs. 
9,10; pl. vi, fig. 3. Specimens with fewer ribs from the Spilsby Sandstone and the Claxby Ironstone 
of Lincolnshire approach P. alternans more nearly than do the specimens from Speeton. 
2 Thid., p. 186, pl. vi, fig. 4. 
3 “Mon. Aptien de l’Espagne’ (1865), p. 92, pl. vii, figs. 5, 6. 
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