l8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I39 



Comparison. — This is a very distinctive little brachiopod and can- 

 not be confused with any other modern form. It is characterized by 

 a yellowish to white and shiny, transparent to translucent shell having 

 peculiar deltidial plates, long, slender maniculifer crura and a short, 

 high, slender median septum. The only described genus similar to it 

 is Mannia which is said to differ in the form of the septum and the 

 possible presence of spines on the exterior. (See Mannia.) 



Cryptopora has frequently been compared with the Triassic genus 

 Dimerella but the two are actually very different. The median septum 

 of the brachial valve of Dimerella has a different form, the deltidial 

 region of the Triassic shell is different, and the dental plates are much 

 less strongly developed than those of the modern genus. The exterior 

 of the two genera is also quite different, the Triassic shell being wide 

 with a fairly wide hinge and costellate exterior. The modern genus on 

 the other hand is narrowly triangular and smooth. 



Geological horizon. — Cryptopora was recorded from the Eocene 

 (Salt Mountain formation) by Toulmin (1940, p. 229). It is also 

 known from the Oligocene of Cuba and Miocene of Europe (see below 

 and Mannia). 



Thomson (1927, p. 147) cites Rhynchonella discites Dreger from 

 Vienna, R. lovisati Dreger from Sardinia, and Hemithyris parvillima 

 Sacco from Italy, all from the Miocene, as possible fossil examples of 

 Cryptopora. Thomson also cites Terebratella acutirostra Chapman, a 

 possible synonym of C. brazeri from the Miocene of Victoria, Aus- 

 tralia, as another fossil species. The geological range is therefore 

 from Eocene to Recent. 



Distribution. — In the North Sea and North Atlantic south to Cuba 

 in waters ranging from 75 to 2,200 fathoms. In the Southern Hemi- 

 sphere it occurs off New South Wales in 17 to 100 fathoms, and on 

 southern Agulhas Bank, South Africa, in 500 to 565 meters or about 

 275 fathoms. 



Assigned species. — The one Eocene form known was not named 

 but species are known from the Miocene and in modern waters : 



Atretia gnomon Jeffreys, Recent, North Atlantic. 



A. brazeri Davidson, Recent, east Australia. 



Cryptopora boettgeri Helmcke, Recent, southern Agulhas Bank, Africa. 



C. rectimarginata Cooper, Recent, East coast Florida, Cuba. 



? Rhynchonella discites Dreger, Miocene, Vienna. 



? R. lovisati Dreger, Miocene, Sardinia. 



? Terebratella acutirostra Chapman, Miocene, Australia. 



? Hemithyris parvillima Sacco, Miocene, Italy. 

 Mannia nysti Davidson, Miocene, Belgium. 



