ORDER in TELEODESMACEA 



anterior and posterior laterals in the right valve only. Flcctwlun, Carp. ; surface granul:it-l. 

 Jihinoclama, D. and S. ; like Plectodon, lint \vithmit cardinal teeth. TV///////,, ///,/, D. and 

 S. ; hin^e with ;i buttress, one anterior canlinal, hut no lateral in either valve. 

 1 ). and S. ; right valve with a single cardinal, no other teeth in i-itln-r \al\i . 

 laminar buttress in each valve. Luzonia, Dall. Tertiary and Recent. 



Myonera, Dall and Smith. Shell thin with concent ric waves and sparse radial 

 ribs; hinge edentulous ; rostrum short, rounded. Kecent, al>\>.-al. 



ICorburella, Lycett. Middle Jura. >'/*////..//>/>, Saiilbt-i^-r. T-rtiary. 



Order 3. TELEODESMACEA. Dall. 



A. PANTODONTA. 

 Laterals exceed im/ fn'n in any one group. 



Family 1. Allodesmidae. Dall. (Cycloconchidae, Ulrich). 



Shell rounded; valves equal, free, closed, with feeble concentric sculpture; area 

 linear, amphidetic ; ligament sub-external, parivincular, opisthodetic ; adductor scars 

 sub-equal, pedal scars above and distinct from the adductors ; pallial line entire ; hinge 

 with one or two lateral laminae on each side of the beak, the posterior below the ligament, 

 received into corresponding grooves on the right valve ; cardinal teeth radially grooved ; 

 one or two in each valve, those in the right valve stronger. Silurian. 



This family, as suggested by Neumayr, probably exemplifies the first step in the develop- 

 ment of the Teleodesmacean hinge. But it must be admitted that its amphidetic though 

 linear area, the occasional multiplication to three of the lateral laminae, and the sub-ligament- 

 ary location of the hinder laminae, are very reminiscent of the prevalent Silurian Schizodont 

 type, and the family can be admitted to the Teleodesmacea only as a probable ancestor, rather 

 than a perfectly developed type of the modern assemblage. 



Orthodontiscus, Meek (Gycloconcha, Miller ; ? Anodontopsis, M'Coy). Silurian ; 

 Ohio. 



Allodesma, Ulrich. Like Orthodontiscus, but more elongate, the beaks more 

 anterior, the anterior adductor scar buttressed by a radial ridge, and the anterior 

 lateral teeth short or absent. Ordovician. 



B. DlOGENODONTA. 



Laterals normally one or two, and cardinals three or less, in any one groi'j>. 



Superfamily 1. CYPRICARDIACEA. Dall. 



Lobes of the mantle partly closed ventrally ; anterior lateral laminae absent, or 

 grouped with the cardinal teeth, short and obscure. 



Family 2. Pleurophoridae. Dall. 1 



Shell substance cellulo-crystalline ; valves equal, free, closed ; adductor scars sub-equal, 

 free from the pedal scars; pallial line entire, or feebly sinuated ; area obscure; /////- 

 nient external or seated in a groove, parivincular ; margins of the valves usually plain ; 

 hinge with one left and two right posterior laminae, the anterior laminae absent or con- 

 fused with the cardinals ; two or three cardinal teeth in each valve, of which the posterior 

 in both valves is sub-parallel to the dorsal shell margin, and in the right valve is usually 

 bifid. Mantle with a moderate pedal and two siphonal openings, the latter usual I >i nt 

 produced into tubes. Devonian to Recent. 



1 Cyprinidae, p.p. of authors, but this name cannot be used. 



