104 PROCEEDINGS OF WASHINGTON MEETING. 



of his work seems to be that he is inclined to limit specific variation within much 

 narrower limits than do many workers on the echinoids. In the larger faunas from 

 the upper Cretaceous, as in that from New Jersey, the whole of the species are pe- 

 culiar to America, and in most cases the species are quite distinct from their Euro- 

 pean representatives. The abundance and variety of the species of Cassidulus is the 

 most striking feature in this upper Cretaceous fauna, and they are all quite distinct 

 from the European species. Dr. Clark does not admit one species as occurring in 

 the eastern hemisphere (excluding, of course, those described by M. Cotteau), and. 

 so far as I have been able to examine the American collections, 1 am inclined to 

 agree with him except, possibly, in the case of Holaster simplex, Shum. \ II. coman- 

 chesi, Marc), from the Comanche series of Fort Worth. Texas. There are two good 

 specimens of this species in the American Museum of Natural History, New York. 

 These seem to be indistinguishable from the European 77. Ixiris (De Luc), a very 

 variable species in which several well characterized varieties are recognized. 

 The same variations seem to occur in the American forms, and one of the two is our 

 H. Isevis, var. trecensis, the other being II. Ixvis, var. planus. Other species from the 

 ( 'oinanche series are very different from the European ones — e. g., the Goniopygus 

 zitteli, Clark, and Holectypus planatus, Roemer. The latter is an interesting species, 

 as its ornamentation rather resembles that of the Jurassic forms. The resurrection 

 of the fifth genital pore is also noteworthy, as it happens in Europe in some allied 

 genera of the same age. 



Hence in the American Cretaceous echinoidea we find the relations to their 

 European representatives to indicate that the two faunas were very closely allied 

 in the lowest Cretaceous, but that in later periods of this age the two faunas devel- 

 oped on independent lines. The evidence of this system is of especial value, as in 

 Europe there is practically a complete series of echinoid faunas from the Valangian 

 to the Danian, and thus the difference between these and the upper American 

 faunas cannot he ascribed to differences of age. The New Jersey Middle marl 

 fauna must be not only homotaxial but synchronous with some of the echinoids 

 between the Gault and the upper ( Ihalk. 



Eocene axd^Ougocexe Faunas. 



A list of the paleogene echinoids from the United States, copied from existing 

 literature, would give but a poor idea of the composition of this fauna or of its 

 afiinities. The whole group is in urgent need of revision, and it certainly does not 

 seem a sparse one. Thus, the collection of the American Museum of Natural His- 

 tory includes species of Sarsella, Euspatangus, and Breynella* none of which have 

 been previously recorded from America. The Smithsonian Institution collections 

 also add the genera Cidaris and Echinarachnius, and the Academy of Natural Sci- 

 ences the genus Monostychia. 



The most striking feature in the echinoid faunas of these two systems is the pre- 

 dominance of the group of flat clypeastroidea, belonging to the genera Mortonia, 

 l'< riarchus, Echinanthus ( Leske non Breynius), Scutella and Echinarachnius, and of the 

 numerous species of Cassidulus and Pygorhynchus. The great series of spatangoids 

 found in the European Eocenes are hardly represented. The abundance of the 

 two last genera mentioned is of interest, as they were common forms in the Ameri- 



* The Echinanthus of MM. de Loriol and Cotteau, but not of Alexander Agassiz and other American 

 authors. See a discussion of this question in a paper, now in the press, by the present writer, on 

 tin/ Maltese echinoids, in the Trans Roy. Soc. Edinb. 



