CONCHIFERA. 



283 



slender, unequal siphonal tubes ; foot and palpi like those 

 of Nucula* — Several species. 



Two British species, L. caudata and pygmcea, are deli- 

 cate, rostrated shells of small size ; they are found also 

 on the shores of northern countries. 



Yoldia. Moeller. — Shell transversely oval, often 

 lengthened, thin, fragile, with a smooth, polished epi- 

 dermis; gaping at both ends, more behind than before, 

 the margins smooth ; the pallial impression with a sinus 

 behind. Animal with the mantle entirely open before, 

 behind lengthened into two long, curved tubes, ciliated at 

 their edges ; foot large and strong. — 1 species ; also fossil. 



Y. (Nucula), arctica of Gray, is the recent species. 



Malletia. Desmoulins. (Solenella Sow. ; Cteno- 

 concha Gray.)— Shell lon- 

 gitudinally oval, equivalve, 

 nearly equilateral, com- 

 pressed, shining, covered 

 with a thin, olive green epi- 

 dermis; no cardinal teeth, 

 and in each valve only three 

 or four very small anterior 

 lateral teeth, the posterior 



•■ i , Malletia Worrissii. 



lateral teeth numerous, 



small, and sharp pointed, fitting into those of the opposite 

 valve ; a large sinus in the mantle. Animal (according to 

 D'Orb.) having the mantle open in its whole length, be- 

 hind prolonged into two separate tubes ; the gills like two 

 lateral bands; the mouth tentacles long, pointed; foot 

 compressed, broad, capable of being enlarged at the end. 

 — 1 species. 



Mr. Cuming brought M. Norrisii from Valparaiso. 



* Forbes's British Moll. 



