ORDER IL ANOMALODESMACEA 387 
The recent families, Prasinédae and Modiolarcidae, if their validity be confirmed, 

Fic. 685. 
Congeria subglobosa, Partsch sp. Upper Miocene ; Inzersdorf, near Vienna. 
may find a place in this vicinity. Prasina and Berthelinia are reported from the 
Tertiary. 
Order 2. ANOMALODESMACHA. Dall. 
Superfamily 1. ANATINACEA. Dall. 
Anomalodesmacea with V-shaped reticulate gills not secreting a calcareous tube exterior 
to the shell. 
This group is divisible into sections as follows :—(a) Husiphonia, 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 (b) 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 obscure projection or edentulous, the cardinal 
border of one valve covering that of the other valve, which is supplemented by a sort of 
laminar nymph, the ligament sub-internal between 
them; «area inconstant or obscure; pallial sinus 
present ; valves closed or slightly gaping. Trias to 
Lower Cretaceous. 
Plewromya, Ag. (Myacttes, auct.), (Figs. 686, 687). 
Posterior side longer, somewhat gaping, 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. 
rresslya, Ag. (Fig. 688). Like Plewromya, but 

Fic. 686. 
the right hinge margin projecting over the left, — pjewromya peregrina, Orb. Upper Jura: 
. . . . . . Y “, ~ =A r ear <7 r apne 
anterior side short, wide; ligament parivincular, Chorostkow, near Moscow. 4, Internal 
2 A east, 1/;. B, Hinge. 
almost internal, attached to an internal nymph- 
like callosity in the right valve, which appears as a groove on internal casts. Abundant 
in the Jura, especially in the Lias. 
