54 8 TRANSACTIONS OF THE WAGNER FREE 



t 



Through the misunderstanding of an ironical remark in the original de- 

 scription of this remarkable genus, Dr. Fischer was led to suppose that the 

 writer regarded it as the representative of a new order, which was not the case. 

 It is evidently the last term in a series beginning with forms like Lepton and 

 carried on by Galeonnna and Eplnppodonta, but the specialization has been 

 carried so far that it may well be regarded as the type of a distinct family. 



FAMILY KELLIELLID^? 



Soft parts (so far as known) as in Leptonidte, but the mantle plain edged, 

 and contained wholly within the valves ; monoecious ? marine. 



Shell with a periostracum ; valves equal, free, closed, smooth externally 

 with plain margins ; pallial line simple ; area obscure or none ; ligament ex- 

 ternal, parivincular ; resilium external or slightly sunken ; hinge-plate narrow, 

 entire, with one or two cardinals, and a single anterior lateral placed above the 

 anterior cardinal tooth. 



Tertiary and recent faunas. 

 Ex. Kelliella, Luletia, Allopagus, t Turlonia. 



These minute shells are in need of further study. Verrill figures the 

 posterior adductor scar in Turtonia as double ; if the upper be regarded as a 

 pedal scar it will follow that the pedal is larger than the adductor. 



The Austral Cyamium appears to belong elsewhere, but conclusions 

 regarding many of the small forms here included in the Leptonacea must be 

 regarded as only tentative. 



In 1889 I included Kelliella in the Isocardiidcs, in the absence of infor- 

 mation necessary for its proper classification, but the teeth are as much Lep- 

 tonoid as cyclodont, and the general characters, if correctly stated in the Man- 

 ual, point to its inclusion hereabouts. 



O. Oyclodonta. 



Teeth arched, springing from below the hinge-margin, with the hinge- 

 plate obscure or absent. 



Superfamily CARDIACEA. 



Lobes of the mantle free behind the siphons, foot elongate, geniculate; 

 sculpture of the shell chiefly radial ; cardinal teeth conical, the lateral lamina; 

 short, distant from the cardinals. 



FAMILY CARDIID^E. 



Gills with a very simple type of reticulation, strongly plicate, sometimes 

 with the outer limb much produced dorsally; anal chamber completely cut 

 off from the pedal ; siphonal septum sometimes much produced anteriorly above 

 the gills; palps large, not united distally; foot usually keeled, with a byssal 

 sinus, but the byssus usually obsolete ; grooved, capable of being flattened to 



