THE 
GEOLOGICAL MAGAZINE. 
NEW SERIES. DECADE II. VOL. IV. 
No. II.— FEBRUARY, 1877. 
OIKia-ITST-A-Ij AETICLBS. 
I. — On sojie New Pycnodonts. 
By Sir Philip Grey-Egertox, Bart., M.P., F.E.S., F.G.S. 
(PLATES III. axd IV.) 
1. Ccelodus ellipticüs, Egerton. PI. III. Fig. 1. 
Mr. Alfred Crayen, who for some montbs past lias been occupied 
in making a collection of tke organic remains found in tke Gault at 
Folkestone, has submitted to me for examination and description 
(if requisite) a specimen of a Pycnodont jaw wkick, both for tbe 
perfect condition in wbicb it is preserved and for tbe peculiarity of 
its cbaracters, is wortby botb of description and representation. The 
specimen is tbe right mandible with most of the tritoral teeth pre- 
served in their natural position. It betokens a fish of the largest 
size of the family to which it belongs. rivalling in this respect even 
the Pycnodus gigas of the Jura beds. The symphyseal border (PI. III. 
Fig. 1 s) measures two inches and eigbt-tenths of an inch in length, 
and half an inch in thickness. As the anterior extremity is wanting, 
the natural size was probably half an inch longer. The outer 
margin of the jaw measures four inches, and the basal line — connect- 
ing the outer and symphyseal elements of the triangle — three inches 
and two-tenths. The dental armature is composed of four ranks on 
the anterior and three on the posterior area of the mandible. The 
inner row (PI. III. Fig. 1 a ) consists of teeth very considerably larger 
than those of the succeeding rows. Six of these are retained ; but as 
the anterior extremity of the bone is broken, there were probably one 
or two more. The individual teeth measure nine-tenths of an inch 
by four-tenths. They are elliptic in outline, but slightly crescentic 
on the anterior margin. The four anterior plates show progressive 
marks of attrition ; but the fifth and sixth, not having as yet come 
into contact with the vomerine teeth, disclose the peculiar character 
of the dentitipn. This consists in the occurrence of a longitudinal 
sulcus on the anterior face of the tooth, corresponding in form with 
the outline of the tooth, and bordered by a sligbtly crenulated mar- 
gin ; the remaining area of the tooth being perfectly smooth. The 
whole ti;iturating surface is coated with a thick and lustrous enamel. 
The second rank (PI. III. Fig. 1 b ) contains eleven teeth of an 
elongated elliptic form, constricted at the waist, like an hour-glass. 
They measure six-tenths of an inch in length. They are so arranged 
that the alternate teeth are opposite to the intervals between those 
of the inner or principal row. They all have the longitudinal fur- 
DECADE II. — VOL. iv. — xo. II. 4 
