Malletiu.} PELECYPODA. 831 



branchiae narrow, posterior ; foot forming an oval disc with trans- 

 versely striated margins. 



Shell not nacreous inside, oval, compressed, thin, smooth or con- 

 centrically striated, gaping in front and behind, subequilateral, with 

 epidermis ; beaks small, not much raised ; ligament external and 

 elongated, resting on nymphs ; hinge subhorizontal, formed by an 

 anterior and posterior series of teeth which are very fine ; there is no 

 resilium ; muscular scars not much impressed, subequal and sub- 

 circular ; pallial line deeply notched behind ; a linear depression 

 extends from the umbonal cavity to the anterior adductor-scar. 



Distribution. Gulf of Panama, Peru, Chile, Strait of Magellan, 

 New Zealand, Kerguelen Island, mid South Atlantic, Atlantic, West 

 Indies, Japan. From the laminarian zone to about 2,550 fathoms. 



Remarks. In the Cretaceous and Eocene of Patagonia, in the 

 Miocene of Italy and New Zealand. Malletia is a Patagonian genus, 

 having reached the coast of Europe and New Zealand after long 

 migrations. (Dr. H. von Ihering.) 



Subgen. 1. NEILO, A. Adams, 1854. 



Neilo, A. Adams, P.Z.S., 1852 (1854), 93. Type: N. Cumingii, A. Ad. 

 = australis, Q. & G. 



Animal having a double mantle-margin, the outer edge fringed, 

 and furnished behind with ventral lobes ; the siphons are long, slender, 

 united, and retractile ; the labial palps are elongated, fimbriated at 

 their margins, and appendiculate ; the gills are narrow ; and the foot 

 is large, geniculate, compressed, and folded, forming an oval disc 

 with crenate margins. 



Shell transverse, ark-shaped, posteriorly gaping and subtruncate ; 

 surface of valves covered with a thin brown epidermis, concentrically 

 furrowed ; inside not nacreous ; hinge-line nearly straight ; teeth 

 with numerous small acute comb-like denticles ; ligament external, 

 conspicuous ; muscular scars wide apart ; pallial line with a deep 

 sinus. 



This subgenus is known from Malletia by its ark-like form and 

 by the surface of the valves being sculptured. 



Distribution. New Zealand, Gulf of Panama, and off the coast of 

 Ecuador, in 1,672 and 741 fathoms. 



1. Malletia australis, Quoy and Gaimard, 1835. Plate 58, figs. 2, a. 



Nucula australis, Q. & G., Voy. Astrol., iii, 1835, 471, pi. 78, f. 5-10. Dieff. 

 N.Z., 258. Solenella australis, Q. & G., Grit, List, 49 ; Hutton, J. 

 de Conch., 1878, 54 ; M.N.Z.M., 166 ; P.L.S. N.S.W., ix, 529. Neilo 

 australis, Q. & G., Ereb. & Ter., 6, pi. 2, f. 13. Ctenoconcha navicula, 

 Valenciennes, Voy. " Venus," Moll., pi. 23, f. 7. Neilo Cumingii, A. 

 Adams, P.Z.S., 1852 (1854), 93. Solenella Cumingii, A. Ad., G.M.M., 81. 



Shell elongated oblong, equivalve, inequilateral, fairly solid, 

 rounded in front, produced and waved behind, with concentric sharp 



