ORDER III 



TKLKODKSMACKA 



419 



Donax, Linn. (Fig. 771). Anterior -i<l<- lon^n, lateral* weak. rpper Kcei. 

 Recent ; about 100 species. Sub-genus Iphigenia, 



Schum. lien-lit. 



/v/'/'/c, L-a. Lower KIMVIH-. 



Superfamily 14. SOLENACEA. Lamarck 



(emend.) 



Dwellers in soft sea-bottom, narrow, elongated, / miatian 



modified for burrowing, gaping at both ends; foot 8 



elongated, distally modified to serve as a piston or stilt within the burrow ; hinge without 

 lateral laminae. 



Family 37. Solenidae. Leach. 



Shell substance as in Tellina, but the external layer showing its cellular structure 

 more clearly ; with a pronounced epidermis ; valves equal, free, usually truncate at both 

 ends, and more or less inequilateral, ivith low beaks, smooth margins, not rostrate, smooth 

 or feebly sculptured ; adductor scars narrow, elongate, dorsally distributed, pedal distinct; 

 pallial sinus small in species with anterior umbones, and vice versa ; ligament and re- 

 silium external, parivincular, seated on nymphs; area obscure or none; hinge plate 

 hardly developed ; hinge often with a thickened ray crossing the valves and serving as a 

 buttress ; cardinals varying from one to four in each valve, usually a single slender 

 radial laminar cardinal in the right, and two in the left valve, with or without one or 

 two placed parallel with the hinge margin, simulating laterals; radial teeth usually 

 more or less pedunculated, rarely bifid. Devonian to Recent. 



The Silurian forms heretofore referred to this family do not seem to belong to it, but 

 Palaeosolcn, Hall, is scarcely distinguishable externally from some modern forms ; its hinge, 



FIG. 77-.'. 



Sn/r,i xiilifrii-i/Uis, Eichw. Mioceut; (Sanna- 

 tian Stage) ; Pullendorf, Hungary. 



Cultellus GHgnonem-i.^, Hi-sli. Calcaire 

 Orossier ; Grignon, near ParN. 



however, is unknown. The species of this family are mostly much modified for a sp< -rial 

 mode of life, hence the variability in certain features, such as the siphons, foot, and frnna- 



ture of the mantle lobes. Novaculina has been 

 naturalised in fresh water, and Tagelus apprar- t-> 

 prefer estuaries. 



Solen, Linn. (Fig. 772). Scabbard - shaped, 



straight, with terminal beaks. Among tin- nunn-r- 

 ous sub - genera are : Ensis, Sebum. ; Pharella, 

 Gray ; Ceratisolen, Forbes ; Siliqua, Megerle ; Cul- 

 tellus, Schum. (Fig. 773). Tertiary and Rea-nt. 



Palaeosolen, Hall. Devonian. Leptosolen, 

 Conrad. Cretaceous. 

 Solecurtus, Blainv. (Psammosolen, Risso). Cretaceous to Recent. Sub-genera : 

 Madia, Oken (Fig. 774) ; Tagelus, Gray; Novaculina, Benson, fresh water. 



FIG. 774. 



Solecurtus (Macha) Deshayesii, Desm. Cal 

 caire Grossier ; Grignon, near Paris. 1/1- 



