180 PKOr. p. M. DIJNCAlf's EEYISION OF THE 



Peristome slightly excentric in front, deeply sunken, tlie in- 

 terradial margins projecting and tumid. Periproct marginal, 

 moderately large, elliptical, witti a downward projection. 



Fossil. Eocene : Europe. 



II. Eamily Cassidulid^. 



Cassiduloidea with very variably shaped tests ; ambulacra 

 petaloid, subpetaloid, or apetalous dorsally, and with crowded 

 doubling of the pairs of pores close to the peristomial margin, 

 forming with the single swollen and ornamented interradial peri- 

 stomial plates " a floscelle." 



This Eamily contains 27 types, and they may be grouped 

 artificially around four genera. 



Alliance of Genus Cassidulus. 



Subgenus Rhynchopygus. 

 Pyfforhynchus. 

 Genus Stigmatopygus. 

 Echinanthus. 

 Subgenus Hardouinia. 

 Genus Eurhodia. 



Paralampas. 

 AUiance of Genus Catopygus. 



Subgenus Studeria, subgen. no v. 

 Genus Neocatopygus, 

 Phyllobrissus, 

 Alliance of Genus Clypeus. 



Subgenus Clypeopygus. 

 Genus Pygurus. 

 Faujasia. 

 Galeroclypeus. 

 Pseudodesorella. 

 Alliance of Genus Echinolampas. 



Subgenus Milletia. 

 Genus Phylloclypeus. 

 Conolampas, 

 Plesiolampas. 

 Subgenus Oriolampas. 

 Genus Palceolampas. 

 Microlampas. 

 Neolampas. 



A. Agassiz gives some very valuable notes upon the distinction 

 of the genus Cassidulus, Lmk., and the genus RJiyncho^ygus^ 



