464 MOLLUSCA phylum vi 



The Eecent .families, Jiiliidae and Modiolarcidae, if their validity be confirmed, 



Fio. 734. 

 Congeria siibglohusa (Partsch). Upper Miocene ; Inzersdorf, near Vienna. 



may find a place in this vicinity. Julia Gould (Prclsina Desh.), and Berthelinia are 

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



Order 2. ANOMALODESMACEA Dall. 



Superfamily 1. ANATINACEA Dall. 



Anomalodesmacea with \/ -shaped reticulate gills not secretimj a calcareous tube 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 {h) Adelosiploonia, with sliort siphons, the lithodesma dividing 

 the mass of the resilium niesially. 



Section A. Eusiphonia. 

 Family 1. Pleuromyacidae Zittel. 



Shell slightly inequivalve, hinge ivith an obscure projection or edentulous, the cardinal 

 border of one valve covering that of the other valve, which is swpplcmented by a sort of 

 A laminar nympih, the ligament sub-internal between 



them ; area inconstant or obscure ; pallial sinus 

 present ; valves closed or slightly gaping. Trias to 

 Lower Cretaceous. 



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

 Posterior side longer, somewhat gaj^ing, hinge 

 margin with a thin horizontal lamina in each 

 valve, the left inferior, the margin with a feeble 

 notch behind the lamina ; ligament parivincular. 

 Trias to Lower Cretaceous ; abundant, but seldom 

 well preserved. 



Gresslya Ag. (Fig. 737). Like Pleuromya, but 

 the right hinge margin projecting over the left, 

 anterior side sliort, wide ; ligament parivincular, 

 almost internal, attached to an internal nymjih- 



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



Abundant in thci Jura, especially in the Lias. 



Flii. 735. 



Pleuromya peregrina d'Orh. Upper .hira ; 

 ChorostUi'iw, near Moscow. A, Internal 

 mould, i/i- i'l Hinge. 



