l8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I44 



only in having an inframarginal pcriproct. Faurastcr may be related 

 to Hardonhna in having similar wide petals, a supramarginal peri- 

 proct, and strong bourrelets, but until something is known of its 

 phyllodes its affinities cannot be determined. Australanthus may be 

 descended from Hardoninia, having strong bourrelets, wide phyl- 

 lodes, equal petals, and a supramarginal periproct. It is more ad- 

 vanced as shown by its monobasal apical system. Stigmatopygus 

 appears to be descended from the same stock as Hardouinia, having 

 a similar large inflated test, supramarginal periproct, broad, closed, 

 equal petals, flat adoral surface, large bourrelets, and broad phyllodes. 

 Gongrochamis is probably descended from Stigmatopygus, differing 

 from it only in having more pores in its phyllodes and a prominent 

 bulge in the median area of each phyllode. Pygnrosioma is related 

 to Gongrochanus, having wide phyllodes with many pores, strong 

 bourrelets, and well-developed petals. Lefortia, Faujasia, Eurype- 

 talum, and Doviechinus appear to be related, all having similar broad 

 petals, wide phyllodes, moderately strong bourrelets, and broad tests 

 of medium size, and may be descended from Pctalohrissns. 



Apparently, the Cassidulidae evolved from the Nucleolitidae, with 

 Nucleopygus originating from Nucleolitcs. The two genera are 

 similar in having a supramarginal periproct and straight, open petals 

 with narrow poriferous zones, but Nucleopygus is more advanced 

 in having single pores in its ambulacral plates beyond the petals and 

 in having buccal pores. Rhynchopygus is similar to Nucleopygus 

 in its small test and petal arrangement but differs in having stronger 

 bourrelets, wider phyllodes, more advanced tuberculation with larger 

 tubercles adorally, and a naked zone in interambulacrum 5. Both 

 Ochetes and Hypsopygaster seem more closely related to Rhyncho- 

 pygus than to Nucleopygus, sharing with Rhynchopygus strong 

 bourrelets, larger tubercles adorally, and a naked pitted zone in 

 interambulacrum 5. Having double pores in its ambulacral plates 

 beyond the petals, Ochetes is more primitive than Rhynchopygus, 

 whereas Hypsopygaster with its monobasal apical system is more 

 advanced than Rhynchopygus. Cassidulus is very similar and with 

 little doubt a descendent of Rhynchopygus, from which it differs 

 only in having a monobasal apical system. Rhyncholampas has strong 

 affinities with Cassidulus as shown by the existence of some species 

 with characters intermediate between these two genera. 



The Echinolampadidae are descended from the Nucleolitidae, prob- 

 ably from a genus like Pygorhynchus. The two oldest genera in the 

 family, Arnaudaster and Parapygus, are very similar to Pygorhyn- 



