494 MOLLUSCA phylum vi 



Of the numerous subgenera, Baroda {Fig. 813) and Itscanotia (Fig. 814) Stol., from the 



Cretaceous, are remarkable for their elonga- 

 tion and the riilge-like form of the posterior 

 cardinal. 



Onco'phora Rzehak. Differs from Ta2:)es 



in having a very short pallial sinus, and 



the anterior adductor scar bounded by a 



ridge. Miocene brackish-water beds. 



Fio- SI-*- Venenipis Lam. Cardinal teetli 2 : 



Papilla {Iscanotia) impar Zitt. Upper Cretaceous ; 9-3 stron"- • a borer or nestler, often de- 



Gosau. ' n m' - T Ti 



formed. Tertiary and Recent. 



(I. Gemma Desh. ; Parastarte Conr. ; Psephidia Dall. Minute shells. Eocene 

 to Recent. 



Family 32. Petricolidae d'Orbigny. 



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

 with plain margins and inconsp>icuous beaks ; posterior adductor scar larger than the 

 anterior, pedal narroio, elongctted, distinct ; ligament and resilium external ; area 

 obscure or not defined ; hinge without lateral laminae, with tivo or three small, usually 

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



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



The family Glaucomtacidae, 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 bases, usually long ; pallial line sinuate ; ligament external, 

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

 tvjo radicd cardinals, of which the anterior is commonly bifid 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 sliglitUj 

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

 pressed, usually with smooth margins, low beaks, and variable, chiefly concentric sculpture ; 

 anterior adductor scar larger, frequenily irregular ; pedal distinct ; resiliu,m embraced in 

 the ligament, sub-external; area narroio, small, covered with a dark epiidermis, 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: Tellina s.s. (Figs. 815, 816); Tellidora Morch ; SlrUjilla Turton ; Lincaria 

 Conrad {Arcopagia 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 Lye. Long, oval, obliquely truncate behind ; beaks low, 

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



