98 GASTEROPODA OF THE INFERIOR OOLITE. 



The above is in the main the original diagnosis of Morris and Lycett, which 

 had to a certain extent been modified by Piettein 1856. To show the uncertainty 

 which still prevails with regard to the family position of Brachytrema, I would 

 refer to the partial list of genera, p. 12 of this Monograph. It will be seen that 

 Fischer places the genus with a query under Cerithiidge, Tryon places it under 

 Littorinidge or Cerithiidge, Tate under Cerithiidge provisionally, Stoliczka under 

 Cerithiidge. Morris and Lycett, on the other hand, originally regarded it as related 

 to the Muricidae. 



These shells are very scarce and poorly preserved in the Inferior Oolite of 

 England, so that our opportunities for adding to the knowledge we possess of the 

 genus have not been great. Omitting the more fusiform shells which have 

 occasionally been referred to Brachytrema, two distinct groups are apparent, one 

 of which is like Purpuroidea in its aspect (B. Wrightii) ; the other might with 

 more justice be regarded as related to the family of the Cerithiidge (B. subvaricosum). 

 Thus the genus is to be regarded as a composite one, which possibly may be 

 broken up when the subject has been more fully ventilated. 



17. Brachytrema subvaricosum, sp. nov. Plate II, figs. 9 a, b. 



Description : 



Length ..... C'25 mm. 

 Width . . . . .4-12 mm. 



Length of body- whorl to entire shell, about . 50 : 100 



Spiral angle .... 50° 



Shell small, subcorneal, apex pointed. Whorls six, nearly flat, and without 

 strong sutural depressions. The ornaments consist of three stout, undulating 

 spirals, which are wide apart, though somewhat fused together in the apical 

 whorls. In the body- whorl a fourth spiral is developed ; and in the base the 

 spirals are fine and not numerous. The longitudinal ornamentation is irregular 

 and not conspicuous, though slightly variciform in character. 



Aperture subquadrate and somewhat restricted, canal short, columella curved, 

 notch narrow. 



Relations and Distribution. — Brachytrema brevis, Piette (' Bull. Soc. Geol. 

 France,' 2me ser., vol. xiii, p. 564, pi. xv, figs. 21, 22), believed to be nearly 

 the same as Turbo pygmceus, M. and L. (' Great Ool. Moll.,' p. 65, pi. ix, fig. 29), 

 approaches this species very closely. B. subvaricosum is less depressed, and the 

 longitudinal ornamentation is less sharply developed ; the spirals are larger, wider 

 apart, and less numerous than in Turbo pygmaius. B. varicosa, Lye. (' Suppl.,' 



