BIVALVIA. 137 
VERTICORDIA. S&S. Wood, 1844. 
Generic Character. Shell subcircular, equivalved, subequilateral, closed, nacreous ; 
ornamented with radiating costz or striae; umbo subspiral or incurved; hinge narrow, 
with an obtuse tooth in the right valve and a depression in the left for its reception ; 
lunule small, deep-seated, heart-shaped; adductor muscles more or less ovate ; palleal 
line simple or without inflexion; connexus cartilaginous, with a very slight extension 
outside the dorsal margin; an ossicle in the hinge of the living shell. 
Much uncertainty has hitherto existed respecting the position of this genus. Mr, A, 
Adams, when he first described a species which he obtained near the Gotto Islands, 
Japan, considered it to be allied to the Bucardiide (Isocardia), but subsequently, from 
further examination, he says (in the ‘ Annals and Nat. Hist.,’ May, 1863, p. 100), “I may 
take the opportunity of stating that the true position of the genus (Verticordia) is in 
Anatinide and not with Jsocardia, with which in a former communication I had 
associated it. My brother, in examining one of my fresh specimens, has proved the 
existence of an ossicle in the hinge very similar to that in Chamostrea or Cleidotherus.” 
The late Dr. S. P. Woodward and M. Deshayes placed it in the family Zrigoniade. 
In Zrigonia the mantle of the only known recent species is said to be open all round ; foot 
large, long, and geniculate. In Anatinide the genus Lyonsia has an ossicle, but Pandora 
has not; both these genera have a nacreous texture. <Anatina, Thracia, and Cochlodesma 
have an ossicle, but are only partially nacreous. The animals of all these have the 
mantle prolonged into siphons. In Verticordia the shell is nacreous and the hinge has 
an ossicle, but it is one of the Zztegropallealia with a different form of shell, and is more 
or less costated. I do not think it can belong to the Axatinide, though I confess not to 
know its near relations. I would rather place it in a family by itsel{—‘‘Verticordide.”’ 
The genus seems to have some affinity to Poromya, perhaps to Cardilia and Myftili- 
meria, and in its costated form to that of the Carditide. YI am unable to trace 
a connection, however remote, that it could have lad to any ancestral relation of a 
Secondary period. The nearest resemblance in outward appearance is a_ striated 
Isocardia from the Kimmeridge Clay, called Anisocardia, which is not unlike Chama 
arietina, Brocchi, a species belonging to this genus, and a shell that is striated, but 
not costated. The ossicle in the hinge forms the connecting link which this genus is 
supposed to have with the dnatinide.' Respecting the use of this ossicle Mr. Jeffreys 
says, in ‘ Brit. Conch.,’ vol. il, p. 29, “It was conjectured by Clark that it acted like 
1 Tn the ‘ Brit. Mollusca,’ vol. xi, p. 76, it is said, ‘* Professor Lovén has detected a rudimentary ossicle 
in Montacuta bidentata, which appears to Mr. Alder, who has likewise observed it, a mere calcifizatiou 
of the lower part of the ligament. It is so easily detached that very few cabinet specimens ever 
exhibit it.” 
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