494 MOLLUSCA phylüm vi 



Of tlie nunierous subgeiiera, Baroda (Fig. 813) and Iscanotia (Fig. 814) Stol., from the 



Cretaceous, are remarkable tbr their elonga- 

 tioii and tlie ridge-like form of tho posterior 

 Cardinal. 



Onco'phora Rzehak. Differs from Ta2?es 



in having a very sliort pallial sinus, and 



the anterior addiictor scar bounded by a 



ridge. Miocene brackish-water beds. 



Fio- 814. Venempis Lam. Cardinal teeth 2 : 



' Paphia (Iscanotia) impar Zitt. Upper Cretaceous ; 2-3, stronff ; a borer or nestler, often de- 



Gosau. /.im. T 1-, 



formed. Tertiary and Kecent. 



d. Gemma Desli. ; Parastarte Conr. ; Psephidia Dali. Minute Shells. Eocene 

 to Recent. 



Family 32. Petricolidae d'Orbigny. 



Valves, when not distorted, equal, free, somewhat gaping hehind, radiately sculptured 

 with piain margins and inconspicuous heaks ; posterior adductor scar larger tkan the 

 anterior, pedal narrow, elongated, distinct ; ligament and resilium external ; area 

 ohscure or not defined ; hinge without lateral laminae, with two or three small, usually 

 bifid, radial cardinal teeth in each valve. Cretaceous to Recent. 



Petricola Lam. (Choristodon Jonas ; Naranaio Gray) ; Petricolaria Stol. 



The family Glaucomyacidäe, of estuarine or fluviatile habit, appears to be related 

 to Petricola, and includes the Recent Glaucomya (Bronn) Woodward, and Tanysiphon 

 Benson. 



Superfamily 13. TELLINACEA Blainville. 



Siphons distinct to their hases, usually long ; ^aZ^m? line sinuate ; ligament external, 

 seated on nymphs ; hinge typically with an anterior and posterior lateral in each valve, 

 two radial cardinals, of which the anterior is commonly hifid and somewhat pedunculated, 

 and the posterior, as well as the laterals, often obsolete. 



Family 33. Tellinidae Deshayes. 



Shell substance cellulo-crystalline, with an inconspicuous epidermis ; valves slightly 

 unequal, free, rounded in front, more or less rostrate, oblique, and gaping behind, com- 

 pressed, usually loith smooth margins, low beaks, and variable, chießy concentric sculpture ; 

 anterior adductor scar larger, frequently irregulär ; pedal distinct ; resilium embraced in 

 the ligament, sub-external ; area narrow, small, covered with a dark ejndermis, or 

 frequently obsolete ; hinge-plate narrow, anterior laterals approximate, posterior more 

 distant from the cardinals, when present ; cardinal teeth small ; pallial sinus deep, 

 discrepant in the opposite valves. Jura to Recent. 



Tellina Linn. Elongated, the rostrum more or less twisted ; two lateral teeth in 

 each valve ; shell porcellanous. Jura to Recent. 



Subgenera: Teilina s.s. (Figs. 815, 816); Tellidora Mörch ; Strigilla Turton ; Lincaria 

 Conrad (Areopagia d'Orb.) (Fig. 817), etc. 



Macoma Leach. Anal siphon long, branchial very short, hinge without laterals ; 

 shell smooth, earthy, less elongated than in Tellina. Tertiary and Recent. 



Gastrana Schum. {Fragilia Desh.). Miocene and Recent. 



Quenstedtia Mor. and Lyc. Long, oval, obliquely truncate behind ; beaks low, 

 pallial sinus shallow, only a single cardinal tooth present. Jura. 



