25 
P LAG I OSTOM A punctata* 
TAB. CXIII. — Figs. 1 and 2. 
Spec. Char. Depressed, obliquely ob ovate; with 
numerous diverging striae ; anterior side long, 
straight * ears nearly equal ; diverging stride 
transversely marked with other very fine strife, 
or punctums. 
w hen young the margin is rather a greater segment of a 
circle than half, but older shells approach to an oval, the 
greatest length of which is placed obliquely parallel to 
the cavity on the anterior side, in which lies one of the 
ears; the diverging striae are, fine, becoming obscure in 
the older shells ; the transverse ones are hardly to be seen* 
except in the hollows of the others, where they appear as 
minute punctums; in the young shells they undulate, and 
seem like rows of minute punctums across each of the di- 
verging stride. The length and breadth, taken at right 
angles to each other, are nearly equal ; the depth of one 
valve near the beak is about one sixth of the length. 
Having given some of the Plagiostomae in tab. 77 and 78, 
I now add a few more species of this tribe, which it may 
be proper to distinguish, and save some inconvenience to 
the inexperienced : different species having their respective 
localities, they will be better understood. The present 
species has a distinct character in the punctums, as pointed 
out by Miss E. Hill. This is from a quarry, at Pickeridge 
Hill, of hardish light and dark grey Limestone, called 
grey and blue Lias, provincially ; it is a little foetid when 
scraped; has faint impressions of shells much pressed, or 
flattened volutions of Ammonites, which being rather on 
the face of the stone, form a natural resemblance which 
