84 PROCEEDINGS COTTESWOLD CLUB 1905 
of the brachial valve, which in A. subangulata is convex 
from the umbo to about half its length, whence it usually 
becomes slightly concave to the front margin, and in the 
difference in the manner in which the margins of the 
valves become thickened in old age. This latter is an 
extremely well marked feature, and is well shown in 
Dr Haas’ figure. 
The fossil is found in the Ferruginous Limestone— 
Zone of 7metoceras scissum—and throughout the Pea-Grit 
series, and is common wherever the beds are exposed.’ It 
also occurs in a somewhat modified form in the Oolite 
Marl, from which formation in the Stroud district I have a 
number of specimens. 
2. RHYNCHONELLA BUCKMANI,” sp. nov. 
Pl. IIL., figs. 7—9. 
DiaGNosis.—Shell of medium size, ovate, wider than long, 
brachial 
valve with a broad but not prominently elevated mesial 
valves very convex, of about equal convexity 
fold—corresponding sinus in pedicle valve. Beak acute, 
much incurved, overhung by the very prominent umbo, 
Foramen elongate, bounded on each side by narrow 
incomplete deltidial plates, and in front by the umba. 
Beak ridges almost wanting. Ribs prominent, angular, 
extending the entire length of the shell, variable in num- 
ber from sixteen to twenty, of which from five to six 
occupy the mesial fold and sinus. The valves meet in 
front at a very obtuse angle, which in mature specimens 
becomes obsolete, so that the junction forms .an almost 
continuous curve with the two valves. 
The large specimens measure :— 
Length... oes Me. «-3°7 Oi. OPO seen. 
Width ... .. 19mm. 20mm. 18 mm. 
Height... -» I5mm. 14mm. 13 mm. 
1 See Mr L. Richardson, “ Handbook Geol. Cheltenham ” (1904), p. 77 (footnote), 
and p. 243. 
2 In honour of our late Honorary Secretary, Mr S. S. Buckman. 
