4 MR. E. T. NEWTON OX THE OCCURRENCE OF [Feb. I904, 



The specimen is evidently a single segment of a fossil very closely 

 resembling Edestus minor, arid consists of an elongated basal portion 

 bearing at one extremity a smooth, enamelled, and serrated crown. 

 The inferior border of the base is concave from end to end, and the 

 superior border is convex in the same direction. Below the crown 

 the base is flattened on each side and angular at the inferior border. 

 This angularity becomes less marked towards the middle, and the 

 lower border is then more and more rounded to the opposite end, 

 this portion of the base being thicker and deeper than the part 

 which carries the crown. Two or three vascular grooves are seen 

 upon the side, extending from apertures which penetrate to the 

 deeper parts of the base. The whole of the base has an open 

 spongy texture, the interstices being filled with the dark matrix. 



The line of demarcation between the crown and the base is 

 clearly defined by the edge of the enamel, the roughness of the 

 base increasing as it approaches this dividing-line, which is not 

 quite parallel with the lower margin, but approaches it somewhat 

 as it nears the extremity, and then, curving downward, the enamel 

 completely embraces the end of the base, while beyond it extends the 

 distal part of the crown. 



The free cutting-edges of the crown, so far as preserved, are 

 strongly denticulated, there being on the upper margin twelve den- 

 ticles in 14 millimetres. A closer examination with a lens shows 

 that each of these denticles is again divided into three serrations, 

 the median one being about twice as large as the outer two. 80 

 much of the lower margin as is preserved shows six denticles in 



5 millimetres, but there is no evidence of these being serrated. 

 The outer edge of the enamelled crown forms a narrow pointed 



spur, extending in the direction of the elongated base as far as the 

 end of the upper denticulated cutting-edge, but separated from it 

 by a tongue of the roughened base, which passes in between them 

 for about a third of the length of the crown. Probably there is a 

 similar spur of enamel on the opposite side of the tooth, but this is 

 hidden in the matrix. The end of the crown being absent, its 

 form cannot be known, but, judging from what remains, it seems to 

 have resembled that of Edestus minor ; the dotted line in PI. I, fig. 1 

 gives a restoration on this basis. 



Seen from the end, the crown is much compressed, and the 

 section exposed by the broken surface is lenticular (PI. I, fig. 6). 

 Below the broken end the denticles extend quite to the lower margin, 

 and on each side, just above the lowest denticle, is a little rounded 

 cusp. 



"When the specimen is viewed from above, a deep trough is seen 

 to extend throughout its length, excepting the portion occupied by 

 the crown, close to which the trough descends about halfway into 

 the thickness of the base, and becomes deeper as it passes away 

 from the crown, occupying the whole depth at the opposite 

 extremity. This end of the specimen has the two sides very unlike 

 (see PI. I, fig. 1), for, while the side next to the matrix ends in a 

 rounded point, the side freed from matrix is deeply notched. A part 



