XEILO. 54-5) 



Genus MALLETIA, Desnioulins. 



Shell oval, compressed, smooth ; surface of valves covered 

 with an olivaceous epidermis ; interior sub-nacreous. Hinge 

 with the posterior tooth and part of the anterior tooth 

 divided into fine, sharp denticles ; ligament external, elon- 

 gated, prominent. Muscular impressions wide apart; pallial 

 sinus large and deep. 



Syn. Solenella, Sowerhy. Ctenoconcha, Gray. 



Ex. M. Chilensis, Desmoiilins, pi. 126, fig. 6, 6, a. 



The only species of Malletia at present known is from 

 Valparaiso. 



Genus NEILO, H. and A. Adams. 



Shell transverse, Ark-shaped, posteriorly gaping and sub- 

 truncate ; 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. 



Ex. N. Cumingii, A. Adams, pi. 126, fig. 7. Shell, N. 

 Cumingii, fig. 7, a, 7, b. 



The mantle-margin in Neilo is double, and the outer 

 edge is 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 disk 

 with crenate margins. This genus, which is known from 

 Malletia by its Ark-like form, and by the surface of the 



vol. it. 4 B 



