64 
IV-AFFliNlTIKS OF FURYDFSMA, AND CUMl’AIUSON WITIi 
OTHKR GKNERA. 
Morris said Tlarydesma “ ought to be arranged very near to Avicula ” ^ 
[Pteriidse]; Dana saw another relationship — “there are some analogies to 
the shell of a Jfippopus [Tridaenidm], and also to that of a M eleagrina ” 
[Pteriidm]. Stoliczka, no doubt misled by the supposed “gaping” lunule 
and the “strong cardinal tooth,” believed in “ a relation of the genus to 
TridactiO; and Sippopus.”'^ Freeh placed Eurydesma, as Leiomyalina, near 
Myalina [Myalinidae], hut Waagen^ supported the opinion of Morris, “more 
to an affinity with Avicula or the like, more than with any other shell.” 
He also suggested a comparison with Ancella. 
Eurydesma. appears to us to demand a comparison with two genera in 
particular — Mcleagrina and Maccoyella, and to some extent with a third, 
A'ucella. 
(1) Meleagrina. — In well-grown examples of either M. maxhna and 
its variety, Cumingi, or M. margaritifera, good types of the genus, the 
valves are separated along the dorsal margins, leaving a longitudinal wedge- 
shaped gape or area hearing on its sides the remains of valve attachment 
fibres, noAV functionless. The actual line of contact is along the ventral 
edges of the hinge-plates, interrupted in the centre by the semicircular 
downwardly-protruding edge of a spoon-shaped depression, extending across 
the area from anterior to posterior. On the contact margins, and in the 
concealed portion (when the valves are closed) of the spoon-shaped process, the 
attachment fibres are functional. Were the longitudinal wedge-shaped ga])C, 
or area, filled Avith the attachment fibre mass, the latter, according to Dali’s 
terminology, would he called the “ ligament,” and the concealed more linear 
portion along the line of junction of the valves would become the “ resilium,” 
and the spoon-shaped process the “ resilifer.” 
* Morris in Strzelecki — Op. cit., p. 275. 
*Dana in Wilkes — Op. cit., p. 700. 
’Stoliczka^ — Cret. Pelecyp. India, loc. cit., p. 226. 
* VVaagen — Salt Range Fossils, op. cit., p, 138. 
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