24 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I39 



I am indebted to Dr. A. Vandercammen and the officials of the 

 Institute Royal des Sciences Naturelles de Belgique for a very fine 

 specimen of Manilla nysti from the Upper Miocene (Diestien-Sables 

 de Deurne) from Wommelghem, just east of Antwerp, Belgium. 

 When delivered to me the specimen had both valves attached. Its 

 exterior was photographed and then the valves teased apart with only 

 a small fracturing of the anterior margin of the pedicle valve (see 

 pi. 1, A). Inasmuch as this specimen is essentially a topotype and 

 from the only horizon from which the species is known, it gives an 

 authentic check on Davidson's description and figures. 



My obligation to Dr. Vandercammen is still greater because he also 

 sent me notes on Davidson's type lot and an enlarged picture of his 

 types. These and the fine little specimen now make it possible to cor- 

 rect Davidson's description and to refigure the genus with unretouched 

 pictures. The combined result of this reevaluation is to demonstrate 

 beyond reasonable doubt that Mannia is Cryptopora. 



The specimen from Wommelghem is small, having a length of 2.5 

 mm. and a width of 1.8 mm. The outline is elongate triangular, the 

 beak sharply pointed and the deltidial plates strongly elevated. The 

 exterior appears to be completely smooth, without any trace of con- 

 centric, scaly lines or "adpressed spinules." The anterior commissure 

 is rectimarginate. The interior shows a coarse mosaic of shell fibers, 

 a distinctly rhynchonelloid character. 



The striking feature of the pedicle valve of this specimen is the 

 strong elevation of the deltidial plates and the large size of the apical 

 plate. The interior of the. brachial valve is generically exactly like 

 that of modern Cryptopora but specific differences may be readily 

 noted, especially in the crura. These are bowed as in the modern 

 species but the distal expansion is greatly exaggerated in its size and 

 flatness. Furthermore the serrations on its distal extremity are nu- 

 merous and minute (text fig. 1, A). 



Of features recorded by Davidson as characteristic of Mannia I 

 was unable to confirm the presence of a median septum in the apex of 

 the pedicle valve. The triangular plates on the distal extremity of the 

 median septum of the brachial valve were not confirmed and the 

 details of the exterior are not in accordance with Davidson's descrip- 

 tion and figures. 



The information and data furnished me by Dr. Vandercammen in- 

 cluded a photograph of Davidson's type specimens and the label ac- 

 companying them. Five specimens are shown, one complete specimen 

 exactly like that from Wommelghem sent to the U. S. National 



