﻿THE 



GEOLOGICAL MAGAZINE 



NEW SERIES. DECADE II. VOL. IV. 



No. II.— FEBRUARY, 1877. 



I. — On some New Pycnodonts. 



By Sir Philip Grey-Egbrton, Bart., M.P., F.E.S., F.G.S. 



(PLATES III. AND IV.) 



1. CcELODus ELLiPTicus, Egerton. PI. III. Fig. 1. 



Me. Alfred Craven, who for some months past has been occupied 

 in making a collection of the organic remains found in the Gault at 

 Folkestone, has submitted to me for examination and description 

 (if requisite) a specimen of a Pycnodont jaw which, both for the 

 perfect condition in which it is preserved and for the peculiarity of 

 its characters, is worthy both of description and representation. The 

 specimen is the 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 PycnodiLs gig as of the Jura beds. The symphyseal border (PI. Ill, 

 Fig. 1 s) measures two inches and eight-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. Pig. 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 dentition. 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 slightly crenulated mar- 

 gin ; the remaining area of the tooth being perfectly smooth. The 

 whole triturating 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. IT, — NO. II. 4 



