BIVALVIA. 137 



VERTICORDIA. S. Wood, 1844. 



Generic Character. Shell subcircular, equivalved, subequilateral, closed, nacreous ; 

 ornamented with radiating costae 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 BucardiidcB {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 

 Anatinida and not with Isocardia, 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 Cleidofherus.'' 



The late Dr. S. P. Woodward and M. Deshayes placed it in the family Tric/oniadce . 

 In Trigonia the mantle of the only known recent species is said to be open all round; foot 

 large, long, and geniculate. In Anatinidce 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 Integropallealia with a different form of shell, and is more 

 or less costated. I do not think it can belong to the AnatinidcR, though I confess not to 

 know its near relations. I would rather place it in a family by itself — '"'Verticordida.'' 

 The genus seems to have some affinity to Poromya, perhaps to Cardilia and Mytili- 

 meria, and in its costated form to that of the Carditida. I am unable to trace 

 a connection, however remote, that it could have had 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 AnatinidcB} Respecting the use of this ossicle Mr. Jeffreys 

 says, in 'Brit. Conch.,' vol. iii, p. 29, "It was conjectured by Clark that it acted like 



1 In the ' Brit. MoUusca,' vol. xi, p. 76, it is said, " Professor Loven has detected a rudimentary ossicle 

 in Montacuta hidentata, which appears to Mr. Alder, who has likewise observed it, a mere calcification 

 of the lower part of the ligament. It is so easily detached that very few cabinet specimens ever 

 exhibit it," 



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