OF CONCHOLOGY. 71 



"It was published after rny publication of Atretia, but I admit 

 that the latter was not fully described. You are right as to the 

 relationship, if not the identity of these genera." 



It is for naturalists to settle which name should be adopted. 



Atretia gnomon, Jeffreys, west of Ireland, in very deep water. 

 1000 + fms. ? Jeffreys. 



Order LYOPOMATA, Owen. 



Lyopomata, Owen, Enc. Brit. Ed. viii, vol. xv., article Mol- 



lusca, p. 339, 1858. 

 — Pleuropygia, Bronn, Thierr. iii, 1st Abth. p. 301, 1862. 

 = Inarticulata, Huxley, Lect. Class. 1864. Intr. Class. An. 



p. 116, 1869. 

 Arms free, unsupported by shelly apophyses. Intestine open- 

 ing by a lateral anus. Borders of the mantle lobes entirely dis- 

 united. Brachia without a distinct median lobe. Shell in most 

 cases without hinge teeth, articulation, or cardinal process. 



Family CRANIID^E, H. and A. Adams. 

 Craniido?, H. and A. Adams, Gen. Rec. Moll, ii, p. 583, 1858. 



The complete synonymy of this family and its subordinate 

 groups will be found in the Report already alluded to. 



Shell hingeless, without perforation for a pedicel ; attached by 

 the entire surface or by the umbone of the lower valve, or rarely 

 free. Upper valve suborbicular ; lower valve subcircular or 

 more or less pyriform. Four principal muscular impressions in 

 each valve. Shell structure punctate. Arms spiral, free. 

 Mantle extending to the edge of the valves, closely adhering, 

 without setse on the margin. 



Synopsis of the Family. 



.Genus Crania, Retz. Shell attached, upper valve with the 

 muscular impressions usually excavated but occasionally convex, 

 without apophyses of any kind ; inner surface vaulted without 

 septa; impressions of the pallial sinuses flabelliform, separated 

 in the median line in front. Margin of the valves rough, tuber- 

 culose or papillose. Type Crania craniolaris, Lin. == Anomia 

 craniolaris, Lin., S. N. xii, p. 1150, 1767. 



? Subgenus Pseudocrania, McCoy. Shell free, with the pallial 

 impressions fimbriated and confluent in front. Anterior muscu- 

 lar impressions larger than the posterior ones. Margin of the 

 valves smooth. Type Crania antiquissima, Eichwald, sp., Mc- 

 Coy, Annals Nat. Hist, viii, p. 388, 1851. 



