ECIIINOID GENUS ECHINOCOIÎYS

38 J. S. SMISER. — A REVISION OF THE ECHINOID
base is very little usually not at all retracted, and Ihc lower surface is not (jibbuslike
in appearance. The posterior is pointed bluntly, and the posterior slope of
the Side profile is much more gradual than the abrupt anterior slope. Somewhat
variable in size bid the earlier more primitive forms of tlx- Craie de Triviere seem
to have been a trifle larger on a whole than the ordinary brevis of the Craie
d'Obourg. The Craie de Triviere forms range between 65-80 mm. in length;
55-65 mm. in width and 50-60 mm. in height, while (he Craie d'Obourg form
ranges between 60-70 mm. in length, 50-65 mm. in width and 43-53 mm. in
FIG. 19a-e. — Echinocorys brevis. (a) contour (b) transverse profile (c) longitudinal
profile of a specimen from Hie Craie d'Obourg at llarniignies, figured Specimen Musée
d'Histoire Naturelle, Brussels (I.O.(i435). Same specimen figured by Lambert.
height. The contour is commonly a very short posteriorly pointed oval but
sometimes there is an elongation posteriorly especially in the larger more primitive
Triviere forms. Which latter character caused Lambert to call these forms
representatives of E. yibbus var. oviformis.
E. brevis is tr distinct species, occuring very commonly. It forms a connecting
link between some earlier form, probably E. gravesi or a variety, and some
of Hie later common and important species such as E. humilis, pyroniidnlis,
ciplyensis.
OCCURRENCE : Craie de Triviere to some extent but most common
Craie d'Obourg at Harmignies.
in the