145 



Mactra plicataria. PI. 40. Fig. 220. Shell, with one valve dropped 

 to show the compressed cardinal and lateral teeth and central liga- 

 ment-pit. 



Genus 8. LUTRARIA, Lamarck. 



Animal • thick, oblong, with much produced siphonal tubes, united 

 almost to their extremities ; mantle closed except a rather large 

 anterior opening for afoot of considerable dimensions, both it 

 and the siphons partially invested with an epidermic sheath. 

 (Forbes.) 



Shell; equivalve, oblong-ovate, generally rather compressed, gaping 

 at the sides, dirty- white, covered more or less with a brown or 

 olive-brown epidermis ; hinge composed of tivo flat spoon-like 

 teeth and an erect triangular lamina, no lateral teeth. 



A genus of bivalves peculiar to the Eastern Hemisphere, in which the 

 animal commences to invest its elongately produced siphons with an epi- 

 dermic sheath like Mga ; and the shell has a Mya-\ike aspect with a Mac- 

 ^ra-like hinge. Sixteen species are known, all of a sombre colour and 

 compressed oblong form, of which two are British. They bury in soft 

 oozy mud, at low-water mark or at very moderate depths, with the aid of 

 a rather largely-developed foot, and their shells exhibit very little varia- 

 tion of character. Mr. Darwin would probably argue that the absence of 

 Lutrarias on the shores of North America may arise from their having 

 been exterminated in the struggle for life by the giant Mactras of that 

 locality (see ante, p. 143, note). 



The most abnormal species of the genus are those which have been sepa- 

 rated by Dr. Gray under the title of Zenatia, comprising L. acinaces, Des- 

 liayesii, and Camingii. Lutaria lanceolata is the genus Resania of Gray. 



1. acinaces, Quoy. 



2. arcuata, Desh. 



3. australis, id. 



4. Capensis, id. 



5. Cumingiana, id. 



6. curta, id. 



Species. 



7. Deshayesii, Reeve. 



8. disshnilis, Desh. 



9. elliptica, Lam. 



10. elongata, Gray. 



11. impar, DesI/. 



12. maxima, Jonas. 



13. oblonga, Turton. 



14. Philippinarum, Desh. 



15. rhynchcena, Jonas. 



16. Sieboldtii, Desk. 



VOL. II. 



