472 MOLLUSCA phylum vi 



Trajpezimn Huinpli. emend. Megeiie {Lihitina Scliiiiu . ; Cypricardia Lam.). Shell 

 elongate, trai)ezoidal, concentrically, or more rarely radially sculptured, often with a 

 posterior keel ; three cardinal teeth in each valve, the posterior in the right valve 

 often bifid. Jura to Recent. 



Plesiocyprina Munier-Chalm. Jura. Cicatrea Stol. Cretaceous. Goralliofhaga 

 Blainv. Tertiary and Recent. 



Arctica Schum. {Cyclas Brug. ; Cyprina Lam.) (Fig. 751). Oval or rounded, in- 

 flated, concentrically striated ; beaks prominent, curved, cardinals three in each valve, 

 the left posterior often Infid, the middle left cardinal largest, and the posterior ridge-like. 

 Abundant in the Jura and Cretaceous, and represented by one or two living species. 



Venilicardia Stol. (Fig. 752). Cretaceous. Pygocardia Mun.-Chalm. Tertiary. 



Veniclla Stol. {Venilia Morton; (?) Goniosoma Conr.) (Fig. 753). Left valve with 

 the anterior cardinal strong, sub-triangular. Cretaceous and Tertiary. 



Superfamily 2. ASTARTACEA Dall. 



Lohes of the mantle free ventrally ; lateral laminae obscure, when present distant 

 from the cardinals. 



Family 3. Curtonotidae Dall. 



Bhell short and heavy, ivith sub-terminal beaks ; valves free, equal, closed ; area 

 obscure; ligament as in the Astartidae ; adductor scars, especially the anterior, deep; 

 pallial line simple ; hinge plate broad, without lateral laminae ; the formula of the 



cardinals ^-.-z-^.,-:, or ^ftttt^. Devonian and Carboniferous. 

 KlOlO KlUl 



This group is inserted conformably with the opinion of Neumayr, who regards it as the 

 radical of the Astartidae. 



Curtonotus Salter. Oval, cardinal border thick, with one very strong tooth in the 

 left, and a strong anterior and thin posterior tooth in the right valve. Scars of the 

 adductors strong, especially the anterior. Devonian ; England. 



Prosocoelus Keferst. Devonian. Protoschizod us de Kon. Carboniferous. 



Family 4. Astartidae d'Orbigny (emend.). 



I>]idl substance cellulo-crystalline, with a pronounced epidermis; shell rounded or 



sub-triangular, usually with concentric or not radial sculpture ; valves equal or sub-equal, 



free, closed; area distinct; ligament and resilium external, parivincular, opistkodet'ic; 



beaks prosocoelous ; adductor scars sub-equal, loith a distinct anterior pedal scar ; pallial 



line simple; hinge plate distinct, hinge with anterior and posterior 



lateral teeth and their respective sockets, usually more or less obsolete ; 



cardinal teeth not bifid at the summit, the terminal teeth frequently 



obsolete. Lobes of the mantle free ventrally, not produced into siphons. 



Pig. 754. Trias to Recent. 



mM\llmt-f\nt Astarte SfAv. (Crassina Lam.) (Fig. 754). Roundly triangular or 



('icrslioion, "aIsiicc. oval, rather compressed, thick ; smooth or concentrically sculptured ; 

 '•■ lunule impressed ; right anterioi' cardinal strong. 



A nmnher of genera have been associated with Astarte which prolialily belong elsewhere. 

 The following subgenera, however, are wortliy of reeogiiilioii ; Coehistarle Bohin, Prcconia 

 Stol. ; Crass iii.rlhCv>-i.j\e, nnn Guppy (Fig. 755); Promh-ia Bi)liiii. Jura. Erlphyla Gabb. 

 Cretaceous. Grotriania Speyer ; GoodaUia Turtou (Fig. 757) ; Rhcdocyma Dall ; Digitaria 

 Wood (Fig. 75G). Tertiary and Recent. 



