464 MOLLUSCA phylum vi 



The Eeceiit families, Juliidae and Modiolarcidae, if their validity be confirmed, 



Pi(i. 734. 

 Congeria suhglohosa (Partscli). Upper Mioceiie ; Inzersdorf, near Vienna. 



may find a place in tliis vicinity. Julia Gould {Prasina Desh.), and Berthelinia are 

 reported from the Tertiary, the former in the Oligocene of Florida. 



Order 2. ANOMALODBSMACEA DalL 



Superfamily 1. ANATINACEA Dali. 



Anomalodesmacea with \/-shaped reticulate gills not secreting a calcareous tuhe exterior 

 to the shell. 



This group is divisible into sections as follows : — (a) Eusiphonia, with long siphons, and 

 the lithodesma, when present, at the anterior end of the internal resilium, and external to 

 the mass of the resilium ; and (&) Adelosiphonia, with short siphons, the lithodesma dividing 

 the mass of the resilium mesially. 



Section A. Eusiphonia. 



Family 1. Pleuromyacidae Zittel. 



Shell slightly inequivalve, hinge with an ohscure protection or edentulouSj the cardinal 

 horder of one valve covering that of the other valve, ivhich is supplemented hy a sort of 



laminar nymph, the ligament suh-internal hetween 

 them ; area inconstant or ohscure; pallial sinus 

 present ; ralves closed or slightly gaping. Trias to 

 Lower Cretaceous. 



Pleuromya Ag. {Myacites auct.) (Figs. 735, 736). 

 Posterior side longer, somewliat gaping, hinge 

 margin with a thin horizontal lamina in eacli 

 valve, the left inferior, the margin wdtli a feeble 

 notcli behind the lamina ; ligament parivincular. 

 Trias to Lower Cretaceous ; almndant, but seldom 

 .well jjreserved. 



Fkj. 735. Gresslya Ag. (Fig. 737). Like Pleuromija, but 



Pleuromya peregrinaA'Ovh. Upper Jnra ; the right hinge margin proi'ectinff over the left, 



Chorostköw, near Moscow. A, Internal , • ^^ ^ ^ • ^ ^• . • • -, 



mouid, i/i- li, Hinge. anterior side snort, Wide ; ligament parivincular, 



almost internal, attached to an internal nympli- 

 like callosity in the right valve, which appears as a groove on internal moulds. 

 Abundant in the Jura, especially in the Lias. 



