448 GASTEROPODA OF THE INFERIOR OOLITE. 



Description : 



Height . . . . .26 mm. 



Basal diameter . . . .32 mm. 



Spiral angle .... 85°. 



This is a less broadly tabulate form than the one previously described, the 

 whorls being higher and the apex sharper. In some cases also the whorls are 

 more numerous (six to seven). In other respects similar to T. gradus. 



Relations and Distribution. — The figured specimen is from Stoford, and may 

 be taken as the representative of T. affinis. Lycett figured his T. carinata with 

 the fossils of the Sjnnosa-stage. 



As before observed, we are almost entitled to look upon T. calix, T. ajffinis, and 

 T. gradus as varieties of one species ; where T. gradus is a large tabulate form 

 with about six whorls and an obtuse apex, T. affinis is a large subtabulate form 

 with higher whorls and a sharper apex ; whilst T. calix is a small subtabulate form 

 with five whorls and a very obtuse apex. 



389. Trochotoma depeessiuscula, Lycett, 1850. Plate XLI, fig. 10. 



1850. Trochotoma. DEPEESSitrscu^A, Lycett. Ann. Mag. Nat. Hist., 2nd ser., 



vol. vi, p. 417. 



1853. — — — Proc. Cotteswold Nat. Club, 



vol. i, p. 78. 



Cf. also — DiscoiDEA, Romer. Morris and Lycett, Grt. Ool. Moll., 



pt. i, p. 84, pi. X, fig. 10. 



Bibliography, ^x. — T. depressinscula was not accepted by Morris in 1854, nor 

 by Hudleston and Wilson in 1892. The type specimp" is in the Jermyn Street 

 Museum. 



Description : 



Height . . . . .13 mm. 



Basal diameter . . . .24 mm. 



Spiral angle .... 100°. 



" Depressed ; whorls five, narrow and angulated ; ribs below the angle three, 

 above more numerous. Upper surface of the whorls concave, lower flattened ; base 

 striated, excavation large not deep, height half the basal diameter." 



Belations and Distribution. — More depressed even than T. gradus, and less 

 strongly bicarinated. It is nearly related to " T. discoidea, Romer," of the Great 

 Oolite Mollusca, and may be the same as that form. 



