68 
Waageri apparently considered that the hlnnt dental prominence of the right 
valve also fits into a groove of the left articulus. He says : — “ Below and 
somewhat in front of the semicircular prominence of the cardinal margin of 
the lunula, there is a shallow groove into which fits the flattened spoon-shaped 
termination of the blunt tooth of the other valve, not as the teeth of the 
hinges of bivalves generally do, but only being laterally pressed against this 
groove, whilst the vertically projecting margin of the lunula, which forms a 
kind of wing, accommodates itself in the excavation which is exhibited by 
the upper part of the blunt tooth.” 
8. Adductor Scar . — Morris speaks of the “ great muscular impression 
which, instead of being nearly central as in Aricula (including Meleagrina , 
Lam.), is placed anteriorly.” ^ 
We have been able to obtain but little information on this question so 
far as E. cordatum is concerned, and can only assume its position by 
comparison with that of E. hobartense, Johnston, where we have seen a 
rather distinctly marked adductor scar (PI. XXII, fig. 2). Prom this it is 
considered that this adductor in Eurydesma was weak and poorly developed. 
In E. hobartense it occupies the deepest portion of the valves, and 
on casts is shown, to some extent, by the high shoulder-like projection seen 
in the internal casts. The impression extends obliquely across the valve from 
a high dorso-posterior position to a mid-anterior ; below, its outline is sinuous, 
but the ini[)ression expands antero-ventrally, and the slightly impressed 
margin curves upwards to join the lower termination of the line of pits 
(p. 59) ; above, the edge is not defined on the specimen. 
The position of this large muscular impression corresponds fairly well 
with that of Meleagrina, although here its position is not constant. 
The suggestion that the adductor was weakly developed receives 
support in that, in Meleagrina maxima, Jameson, the scar varies considerably 
in strength, according to the size and thickness of the valves. 
The older authors referred to the adductor scars, but they have never 
been figured. Morris^ considered the genus Monomyarian, and said, “ its 
great muscular impression is placed anteriorly.” According to "WaageiP 
‘ Morris in Sfcrzelecki — Op. cit., p. 276. 
’ Morris in Strzelecki — Op. cit., p. 276. 
• Waagen — Op. cit., p. 1.38. 
