1016. Phillips — Fossil Pisidia new to Ireland. 103 
finally living specimens were taken in the Thames and 
other EngUsh rivers. It is widely distributed in Europe, 
PisiDiUM PARVULUM Clessin. 
(Plate II., figs. 7 to 14). 
This species is more widely distributed in the Irish rivers 
than P. siipinum, having been found in deposits of the 
Shannon, Suir and Barrow. 
The shell was originally well described in Swedish by 
Westerlund who adopted Clessin's MS. name.^ 
Dr. R. F. Scharff has kindly translated this for me, and 
it reads as follows : — ■ 
" Shell very small., of a rounded egg-shape, very ventricose, finely 
striated, rather glossy, very thin, horn-coloured ; umbones pretty 
close to the centre of the shell, pointed and somewhat projecting ; 
hinge short, narrow and covered in (lit. ' built over ') ; liganienl 
slender ; periphery : edge much curved, anterior edge roundl}^ 
pointed, posterior edge rounded, lower edge much curved ; teeth in 
left-hand valve 2, short, outer one very slender, thin, sharp, low, 
half covered by inner one which is short, slightly curved, fairly high ; 
groove very short and narrow ; lateral teeth simple, rather pointed, 
the anterior more pointed and higher than the posterior ; tooth in 
the right-hand valve slender, a little curved, the posterior portion 
slightly thickened ; lateral teeth double, the outer ones very slender, 
short and very low, inner ones rather pointed but lower than the 
corresponding ones in the left-hand valve ; groove short and fairly 
narrow." 
To this I may add that the umbones frequently, but 
not always, possess appendiculae which are ridge-like along 
the lower edge of the nepionic shell. Most of the specimens 
I have seen could be described as solid rather than thin,* 
and they vary slightly in outline in each locality. 
It is the smallest European species, average specimens 
measuring 175 x 1-5 x 1-2 mm. A large valve from the 
Shannon and some from Grays, Essex, are 2 x I'y^ mm. 
The hinge characters are described in detail by Mr. 
Woodward in his Catalogue (p. 106). A description 
compiled by Mr. Stelfox and myself before we were certain 
that the shell was P. parvulum differs slightly from that 
of Mr. Woodward. We find that in the left valve the 
base of the lower cardinal tooth (c. 2) is not continuous 
^Fauna Moll. Terr, et Fluv. Sveciae, Norvegiai et Daniae," p. 553. 
Stockholm, 1873, 
