LUTRARIA. 3G9 



LUTRARIA, Lamarck. 



Shell oblong, equivalve, inequilateral, gaping at both 

 extremities ; external surface transversely striated or fur- 

 rowed, invested with an epidermis ; edges sharp and 

 smooth ; hinge formed of a more or less prominent spoon- 

 shaped fulcrum in each valve, accompanied in the right one 

 by an erect primary tooth, which locks into a pit with 

 laminar tooth- like edges in the left : the greater part of the 

 fulcrum in each valve is occupied by a wide ligamental pit. 

 Ligament partly internal, partly external. Muscular im- 

 pressions strong ; pallial impression with a deep linguiform 

 sinus. 



Animal thick, oblong, with much-produced siphonal 

 tubes, which are united almost to their extremities. Man- 

 tle closed, except a rather large anterior opening for a foot 

 of considerable dimensions ; both it and the siphons par- 

 tially invested with an epidermic sheath. Orifices of the 

 tube fimbriated. Labial tentacles narrow, triangular, 

 pointed. 



The animals of this genus form large and conspicuous 

 shells, not remarkable for their beauty. They live habitu- 

 ally buried in mud, for the most part near low water, or 

 at very moderate depths. The systematic position of 

 Lutraria has been much disputed. Cuvier, Blainville, and 

 very recently D'Orbigny, have placed it beside Mya^ and 

 in the same family, whilst Linnaeus, Lamarck, and Des- 

 hayes have maintained its near affinity to Mactra. The 

 shell presents considerable resemblances to that of the lat- 

 ter genus, yet the animal is in many resjDects nearly 

 related to that of Mya. We place it for the present in 

 the former group, regarding it as an aberrant form of the 



VOL. 1. 3 b 



