MANUAL OF THE MOLLUSCA. 



end of a spoon-shaped process, p, wMcli originates from beneath 

 the umhonal cavity, pallial line wanting. 



Distribution, 3 species. Inferior Oolite, and Great Oolite."' 

 Maine-et-Loire, Calvados, 13. in, Galicia. 



The internal process of Ehgmus has no analogy with that of 

 the Myce and A7iatinoe, which in them, supports the cartilage, 

 and is an internal prolongation of the hinge ; whilst that of 

 Eligmus gives attachment to the adductor muscle, and arisea 

 from beneath the hinge. Eligmus 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. 



CASSLAisrELLA, Beyrich, 1861. 



Synonym, Grryphorhynchus, Meek, 1864. 



Type, Avicula grj^hoeata, Miinster. 



Shell thick, sub -hemispherical ; right valve flat or convave, 

 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 vnde well-defined cardinal area ; 

 ears sub-equal, not produced. Hinge with several small irre- 

 gular teeth near the middle. Siu'face striated. 



Fossil, 6 species. Upper Trias — L. Lias. Austria, Bavaria, 

 Himalayas. 



Sub-family 4. — Pinniince. 



Genus : — PiNisrA. Sub-genus, Aviculojpinna, Meek. 



Type, Pinna prisca, Miinster. Permian. 



Shell nearly or quite equivalve, beaks not terminal. The 

 general aspect of the shell seems to be intermediate between 

 Pinna and Avicula. 



Tbichites (see p. 420). 



Family III. — MYTiLrD-E.* 



MODIOLAHIA, Beck (Jeffreys, 1863) (see p. 422). 



Derivation, allied to the genus Modiola of Lamarck. 



Example, Mytilus discors, Linne. 



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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