J. W. GREGORY — RELATIONS OF ECHINOID FAUNAS. 103 



North America. In the same way three of the six European Carboniferous genera 

 are peculiar to the Eurasian area. The difference between the two faunas is thus 

 extremely marked, and clearly shows that there was no close connection between 

 the echinoids of the two areas. The absence from Europe of the great family of 

 the Melonitidse is especially striking. 



Permian-Jurassic Faunas. 



Aftei' the Carboniferous system the next fauna of any special value is in the ( !re- 

 taceous. The Permian of both continents yields a few species, hut not sufficient 

 for any definite comparison. The paucity of species in the American Jurassic is 

 also disappointing, as the European echinoids of this age are so exceptionally well 

 known. Descriptions of several species by Professor Clark are now passing through 

 the press and serve to encourage the hope that more may be discovered. As yet, 

 however, the few species known are not sufficient for comparison with the Euro- 

 pean faunas. 



The Cretaceous Faunas. 



The Cretaceous system yields much evidence which has been admirably sum- 

 marized by Professor W. B. Clark in a " Revision of the Cretaceous echinoidea of 

 North America," * issued as a preliminary notice to his forthcoming monograph. In 

 this he enumerates 4.'! species belonging to 19 genera; in addition to this are the 7 

 species described by M. Cotteau from Mexico, including representatives of two 

 other genera ; some new species found by Professor Clark ; and a species of Linthia 

 in the museum of the Boston Natural History Society, which, so far as one can 

 judge from the brief diagnosis of Linthia tumithiln, appears to be new. There are 

 also several more species from South America and the West Indies; the former, 

 however, closely resemble the Mexican species, and the latter are a rather isolated 

 group and may be neglected.! The Cretaceous echinoids of the mainland of North 

 America may therefore be estimated at about 55 species, distributed among L>."> 

 genera. i 



If this fauna be examined as a whole it presents a very familiar fades to a Euro- 

 pean echinologist. Only one genus occurs that is not also found in Europe, while 

 several species are common European forms; but if we separate them into their 

 successive faunas we find one interesting point brought out — i.e^that the members 

 of the earlier faunas agree more closely with the trans-Atlantic species than do 

 those of the upper beds, such as of the Yellow limestone of New Jersey. This is 

 especially well shown by the small fauna described by M. Cotteau from Mexico. 

 This yields six good species, of which three are characteristic of the European 

 lower Cretaceous (Aptien and Urgonien), viz, Diplopodia malbosi, Salenia presten&is 

 and I'itfiiiJixiddHssaussurei. The EnaUaster texanus, moreover, is not unlike some 

 European species, and only the form upon which the late Professor Duncan founded 

 the genus Lani< Ha is quite distinct. The identification of these species rests on the 

 authority of M. < 'otteau ; his opinion is of especial weight, as the general impression 



♦ Johns Hopkins ITniv. Circ. no. 8C, 1891. 



I'I'Im- best known of the South American species is the EnaUaster karstein from Ecuador, 

 described by M. de Loriol. An examination of the type of Spatangua Columbia Lea, now in the 



museum of the Academy of Natural Sciei a in Philadelphia, shows that thej ire identical, and ii 



inn -i then fore be known as EnallasU r columbianus < Lea). 



(The following i the lis! of those recognized in addition to those mentioned in IV"' 

 Clark's " Revision : " Stereocidaris, Dlplopodin, Coptonoma, Lanieria and Cardirwter. 



