40 EOCENE MOLLUSCA. 
tudinally, sometimes the reverse; the ears are slightly unequal, the pedal one being a 
trifle the larger. The shell diverges from the umbo at an angle of about 120°, and 
the divergence of the lines upon the fainter portion of the shell at about 80°. 
The typical specimens of this species are from Selsey, Bracklesham, and Stubbington, 
where they attain to full proportions. There are also specimens found in the London 
clay at Hampstead, assigned to this species ; these are seldom more than half the diameter 
of the Sussex shell, and may be considered as a variety, which I will call corneolus, Pl. IX, 
fig. 7, d. ‘The difference in magnitude would not of itself be sufficient to entitle these shells 
to the position of a variety ;' but there is a slight variation in the right auricle, which is 
rather more rounded, and in some of the specimens the proportions are different, giving 
them a more ovate form.? 
4. Pecren contusernatis, S. Wood. ‘Lab. IX, fig. 8. 
Spec.Char. P. testa tenui, subcorned, orbiculato-depressd, equilateralt, tenuissime striata, 
striis radiatis argutis ; umbonibus acutis ; auriculis subequalibus, superné rectangulis, 
costellatis. 
Shell thin, subcorneous, orbicularly depressed, equilateral, and very finely striated, 
stria thin and radiating, beaks acute ; auricles nearly equal, and prominently radiated or 
costated. 
Diameter, 14th inch. 
Locality. Herne Bay (Edwards). 
This shell appears to present differences sufficient to entitle it to an isolated position : 
the elevated radiations or cost: upon the auricles will distinguish it ; and the whole surface 
is more strongly marked by the fine, divaricating, and curving strie with which it is 
covered, and these extend over the auricles. I have seen but one specimen, which is in 
Mr. Edwards’ cabinet, but this differs so materially that I think it cannot belong to the 
preceding species. The auricles are comparatively much larger than those of corzeus : 
in that shell their length does not exceed «ths of the diameter of the valves, while in 
this species they are {ths ; and although the young shells of Pecten have generally larger 
ears, comparatively, than when full grown, a great difference may be seen in specimens of 
the two species of corresponding size. 
' Since writing the above, I have seen a specimen of this variety in Mr. Wetherell’s cabinet, which 
measures 12 inch in diameter. 
? At p. 72, t. 11, ‘Anim. s. Vert. du Bassin de Par.,’ M. Deshayes has pointed out the confusion that 
exists among species with the above name, and enumerates not less than seven, but which he considers to be 
quite distinct. One of these seven (P. corneus, Melville, pl. 111, figs. 11, 12,) very strongly resembles the 
young state of our shell, corresponding with the Highgate variety (corneolus). 
