TROCHOTOMA. 447 



387. Trochotoma gradus, Veslongclim'nfs, 1842. Inferior Oolite variety. Plate 



XLI, figs. 2 and 3. 



1S42. TnociiOTOMA geadus, DeslongcTiamps. 31em. Soc. Linn. Norm., vol. vii, 



p. lOG, pi. viii, figs. 4 — 7. 



1873. — — — Tawney, Duudry Gasteropoda (p. 



53), 45. 



Syn. DiTEEMAEiA EiCAEiXATA, d'Orlignij. Terr. Jur., vol. ii, p. 380, pi. cccxl, 



figs. 8—11. 



BlbliograpJiij, ^x. — The fossils described under tlie above title are not exactly 

 the same as T. gradus, which in Normandy is regarded as a Liassic species. They 

 are in fact intermediate between T. gradus and T. affinis. 



Description : 



Height ..... 28—30 mm. 

 Basal diameter . . . .40 mm. 



Spiral angle . . . .95°. 



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 carinse 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 TrocJiotoma. All my 

 specimens are from Coker, occurring in beds which yield such an abundance of 

 Cirrus (Murchisonse-zone). Tawney mentions its occurrence at Dundry, but 

 possibly this might be held to include 1\ affinis. 



388. Trochotoma affinis, Deslongchamps, 1842. Plate XLI, fig. 4. 



1842. Teochotoma ArriNis, Deslong champs. Mem. Soc. Linn. Norm., vol. vii, 



p. 1U6, pi. viii, figs. 8—10. 

 Syn. DiTEEMARiA AFriNis, iVOrhigiij/. Terr. Jur., vol. ii, p. 381, pi. cccxli, 



figs. 1—3. 

 — Teochotoma caeinata, Lijcett. Ann. Mag. Nat. Hist., 2nd ser., vol. vi, 



p. 417 ; aud Cotteiwold Hills, pi. iv, 

 fiff. 5. 



