428 MANUAL OF THE MOLLUSCA. 
siphonal tubes (Forbes); gills narrow, plume-like, deeply 
laminated, attached throughout; mantle-margin with small 
ventral lobes forming by their apposition a third siphon. 
Distribution, 80 species. Northern and Arctic Seas, 10— 
180 fathoms. Siberia, Melville Island, Massachusetts, Britain, 
Mediterranean, Cape, Japan, Australia. 
Fossil, 190 species. United States, Europe, South India. 
Sub-genus, Yoldia, Moller (dedicated to the Countess Yoldi). 
Fig. 219. Yoldia n. sp. 3. Antarctic Expedition. 
(From a drawing by Albany Hancock, Esq.) The internal organs are represented, 
as seen through the mantle, on the removal of the right valve. 
a, a, adductors ; p, p, pedal muscles; 7, ligament; g, gills; s, siphons (much con- 
tracted); ¢, c, labial palpi and appendages ; 7, intestine ; f, foot ; x, x, lateral muscles of 
the foot ; m, pallial line. 
Y. myalis, Pl. XVII., Fig. 21. Shell oblong, slightly attenuated 
behind, compressed, smooth or obliquely sculptured, with dark 
olive shining epidermis; external ligament slight; cartilage as 
in Leda; pallial sinus deep. Animal with the branchial and 
anal siphons united, retractile; palpi very large, appendiculate ; 
gills narrow, posterior; foot slightly heeled, deeply grooved, 
its margins crenulated ; intestine lying partly close to the right 
side of the body, and producing an impression in the shell; 
mantle-margim plain in front, frmged behind; destitute of 
ventral lobes. Distribution, Arctic and Antarctic Seas, Green- 
land, Massachusetts, Brazil, Norway, Kamtschatka. Yoldia 
limatula (Fig. 220) has been dredged, alive, by Mr. M‘Andrew, 
on the coast of Finmark. Itis also found in Portland Harbour, 
Massachusetts. The animal is very active, and leaps to an 
astonishing height, exceeding in this faculty the scollop-shells. 
