270 



MANUAL OF THE MOLLUSCA. 



behind ; margins even ; pallial line with a small sinus ; umbonal area with a 

 linear impression joining the anterior adductor. 



Animal furnished with two partially-united, slender, unequal, siphonal 

 tubes (Forbes} ; gills narrow, plume-like, deeply laminated, attached through- 

 out ; mantle-margin with small ventral lobes forming by their apposition a 

 third siphon. 



Distr. 30 sp. Northern and Arctic Seas , 10180 fms. Siberia, Mel- 

 ville Id. Mass. Brit. Medit. Cape, Japan, Australia. 



Fossil, 110 sp. U. S. Europe; S. India. 



Fig. 182. Yoldian. sp. -f- Antarctic Expedition. 



fFrom 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; m, pallial line. 



Sub-genus, Yoldia, Holier (dedicated to the Countess Yoldi). Y. myalis, 

 PI. 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-margin plain in front, fringed 

 behind ; destitute of ventral lobes. Distr. Arctic and Antarctic Seas ; Green- 

 land, Mass. Brazil; Norway, Kamtschatka. Fossil, Miocene . (Crag and 

 Glacial deposits.) England, Belgium. 



SOLENELLA, Sowerby. 



Type, S. Norrisii, PL XVII. fig. 22. S. ornata, fig. 23. 

 Syn. Malletia, Desm. Ctenoconeha, Gray. Neilo, Adams. 



