82 MOLLUSCA FROM THE GREAT OOLITE. 
TROCHOTOMA ACUMINATA, Des/. Plate X, figs. 18a, 20. 
TROCHOTOMA ACUMINATA, Deslongchamps. 1842. Mém. Soc. Linn. de Normandie, 
tom. vii, p. 108, pl. 8, figs. 11—15. 
DITREMARIA ACUMINATA, D’Orb. 1850, Prod. Paléont., p. 301. 
T. Testd conicd, spird plus minusve elatd, levi aut substriatd; apice acuminato ; 
anfractibus (7, 8) ex apice ad aperturam magis é magis tumescentibus donec ultimus sub- 
quadratus fiat ; infind facie dilatatd, in medio cavum infunbibuliformem ferente, ad peri- 
pheriam concentrice striaté. (Deslongchamps.) 
Shell conical, spire more or less elevated, smooth, or slightly striated; apex acute ; 
whorls (7, 8) gradually increasing from the apex until the last whorl becomes subquadrate ; 
the lower surface has a very deep but somewhat contracted cavity, which is concentrically 
striated. 
This is the most elevated or conical of the Great Oolite species. The last volution is 
distinctly striated, the rib posterior to the aperture being very prominent ; the height and 
basal diameter are about equal. 
Locality. Great Oolite of Minchmhampton and Bussage ; Langrune, France. 
TRrocHoroMa conuLorpEs, Des/. Plate X, fig. 16. 
TROCHOTOMA CONULOTDES, Deslongchamps. 1842. Mém. Soc. Linn. de Normandie, 
tom. vil, p. 109, pl. 8, figs. 16—19. 
DITREMARIA -- D Orb. Prod. Paléont., p. 301. 
T. Testa conicd, apice acuto; anfractibus (5, 6) concentricé striatis, planis; ultimo 
anfractu vie ad fissuram dilatato ; basi ad peripheriam convewxiusculd, striatd, in medio 
profunde excavata. 
Shell regularly conical, apex acute; whorls (5, 6) concentrically striated, flattened ; 
the lower surface convex, striated, and deeply excavated. 
The volutions are narrow and flattened, the encircling rib narrow and elevated; the 
figure is very oblique, the basal diameter exceeds the height by one fourth. 
Our figure is somewhat reduced. 
Locality. Great Oolite of Minchmhampton and Bussage ; Luc, Langrune, France. 
