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MANUAL OF THE MOLLUSC A. 



siphonal tubes (Forbes) ; gills narrow, plume-like, deeply 

 laminated, attached tbrougbout ; 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. I'oMk n. sp. -I". 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 ; I, ligament ; g, gills ; s, siphons (much con- 

 tracted) ; t, c, labial palpi and appendages ; i, intestine ; /, foot ; x, x, lateral muscles of 

 the foot ; to, pallial luie. 



Y. myalis, PL XYII., 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-margin plain in front, fringed 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. It is also found in Portland Harbour, 

 Massachusetts. The animal is very active, and leaps to an 

 astonishing height, exceeding in this faculty the scollop-shells. 



