5-3 
(b) Besilifer. — This most important functional space is similar in 
both valves, transversely elongated, concave, and roughly scythe-shaped ; it 
commences in both valves immediately below the apices of the umhones, and 
in the left valve is anteriorly cut off from the lunule by an ill-defined ridge 
uniting the umbo Avith the cardinal fold, but leaving the umbonal apex free ; 
the margins of the resilifer are acute and erect in both valves, and gradually 
taper off towards the rounded junctions of the dorso-posterior margins. In 
the right valve the resilifer tapers to a finely drawn out termination beneath 
the umbo, consequently the umbonal region of‘ the area in the left A'alve is 
somewhat wider than in the right. 
Morris spoke of the ligamental area as “ elongate and almost wholly 
internal,”^ hearing numerous resilium furrows, wide, massive, and posterior 
to the umbos. 
This massive area is again seen in Dana’s figure of a portion of the 
hinge of E. saccnlus, McCoy, sp.‘^ Dana says, “ the hinge in the left valve is 
simply a broad, waved surface.” 
This area is likewise shown by Johnston in the Tasmanian specimens 
of E. cordata, Morris,^ but the resilium furrows are only indifferently 
preserved, and in both of Freeh’s figures this grooved area is visible. 
Dr. M^aagen speaks of tbe “ ligament ” in the right A^alve of 
E. glohosum, 'VYaageu, as occujAying “ a sharp, but not very deep groove, 
which, extending in a somewhat sloping direction backwards, gets by degrees 
shallower and broader, and has evidently served for insertion of the 
ligament.”* * It is assumed that “ligament” is used in its old acceptance, 
and not as distinguished from the term “ cartilage.” In the left valve of 
E. glohosum, M^aagen, the “ ligament ” is held in the upper and broader part 
of a bifurcating groove, directed posteriorly, and just below the umbo.® 
c. Byssal Sinus. — -The byssal sinus is a very marked feature in the 
right valve of Eurydesma. It extends from the apex of the umbo to the 
ventral margin of the hinge-plate ; slightly carved and obliquely directed 
posteriorly, forming a moderately deep channel. 
' Morris in Strzelecki — Op. cit., p. 275, PI. XII. 
Dana— Op. cit., p. 699, PI. VII, fig. 8c. 
* Johnston — Syst. Acc. Geol. Tas., PI. XVII, figs. 2, 3 a-c. 
* Waagen — Salt Range Fossils, op. cit., p. 139. 
* Dali — Trans. Wagner Free Inst. Sci., 1895, III, Pt. 3, p. 490. 
