TROCHOTOMA. 447 
387. TrocHoToMa GRADUS, Deslongchamps, 1842. Inferior Oolite variety. Plate 
XLI, figs. 2 and 3. 
1842. Trocuoroma e@rapus, Deslongchamps. Mém. Soc. Linn. Norm., vol. vii, 
p- 106, pl. viii, figs. 4—7. 
1873. — — -_- Tawney, Dundry Gasteropoda (p. 
53), 45. 
Syn. Dirremarta Bicarrnara, d’Orbigny. Terr. Jur., vol. ii, p. 380, pl. ecexl, 
figs. 8—11. 
Bibliography, Sc.—The fossils described under the above title are not exactly 
the same as 7’. gradus, which in Normandy is regarded as a Liassic species. They 
are in fact intermediate between 7’. gradus and T. afjinis. 
Description : 
Height . : : : . 28—30 mm. 
Basal diameter ' : F . AO mm. 
Spiral angle : : gowe 
Shell trochiform and broadly tabulate, with a somewhat obtuse apex; whorls 
of the spire almost rectangular and increasing by wide steps, being strongly 
angulated towards the middle. The ornaments consist of regular spiral lines, 
which pervade the entire shell and are somewhat wide apart; the lines are 
decussated obliquely. Sutures close. 
The body-whorl is strongly bicarinate, the anterior carina forming a blunt 
angle at the periphery, whilst the space between the carine is considerably 
excavated. The base is infundibuliform and rounded towards the periphery, which 
is striated like the spire. Aperture for the most part concealed in all specimens 
available to me. 
Relations and Distribution.—This is a tabulate form of Trochotoma. All my 
specimens are from Coker, occurring in beds which yield such an abundance of 
Cirrus (Murchisone-zone). Tawney mentions its occurrence at Dundry, but 
possibly this might be held to include 1’. affinis. 
388. TrocHoToma arrinis, Deslongchamps, 1842. Plate XLI, fig. 4. 
1842. Trocnoroma arrinis, Deslongchamps. Mém. Soc. Linn. Norm., vol. vii, 
p- 106, pl. viii, figs. S—10. 
Syn. Dirremanrta aFrints, d'Orbigny. Terr. Jur., vol. ii, p. 381, pl. ceexli, 
figs. 1—3. 
a TrocHoroma carinata, Lycett. Ann. Mag. Nat. Hist., 2nd ser., vol. vi, 
p- 417; and Cotteswold Hills, pl. iv, 
S 4 
fig. o. 
