MANUAL OF THE MOLLUSCA. 
end of a spoon-shaped process, », which originates from beneath 
the umbonal cavity, pallial line wanting. 
Distribution, 3 species. Inferior Oolite, and Great Oolite. 
Maine-et-Loire, Calvados, E,. in, Galicia. 
The internal process of Eligmus has no analogy with that of 
the Myce and Anatine, which in them supports the cartilage, 
and is an internal prolongation of the hinge; whilst that of 
Elignus gives attachment to the adductor muscle, and arises 
from beneath the hinge. JLligmus is related through Vulsella 
Turonensis, Dujardin, to Vulsella; the test, however, is not 
fibrous, and M. Munier supposes that the internal nacreous 
layer has been destroyed by fossilization. 
CASSIANELLA, Beyrich, 1861. 
Synonym, Gryphorhynchus, Meek, 1864. 
Type, Avicula gryphceata, Minster. 
Shell thick, sub-hemispherical; right valve flat or convaye, 
the left very gibbous; no defined byssal sinus. Umbones 
sub-central, hinge line equalling the greatest length of the 
shell, in both valves with a wide well-defined cardinal area ; 
ears sub-equal, not produced. Hinge with several small irre- 
gular teeth near the middle. Surface striated. 
Fossil, 6 species. Upper Trias— L. Lias. Austria, Bayaria, 
Himalayas. : 
Sub-family 4.—Pinniine. 
Genus:—PInNA. Sub-genus, Aviculopinna, Meek. 
Type, Pinna prisca, Minster. Permian. 
Shell nearly or quite equivalve, beaks not terminal. The 
general aspect of the shell seems to be intermediate between 
_ Pinna and Avicula. 
TRICHITES (see p. 420). 
Faminy IIl.—Myrininz.* 
MopioLaRiA, Beck (Jeffreys, 1863) (see p. 422). 
Derivation, allied to the genus Modiola of Lamarck. 
Example, Mytilus discors, Linné. 
Synonyms, Lanistes, Humphreys ; Lanistina, Gray. 
Animal with the mantle folded in front into a wide incur- 
rent tube, and behind into a conical excurrent tube ; foot strap- 
shaped. 
Shell rhomboidal, sculptured by two rows (one on each side) 
* See p. 420. 
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