DISTRIBUTION OF MESOZOIC AND OENOZOIG ECHINODERMATA 687 



The Cretaceous echinoderins are very numerous in certain areas. A great 

 variety of types is represented and the material is oftentimes splendidly pre- 

 served. Many of the species are narrowly limited in geological range and 

 therefore are important as type fossils. 



The crinoids are represented by Uintacrinus, Pentacrinus, and Rhizocrinus, 

 this first genus having afforded a great number of remarkable specimens in 

 the Niobrara chalk of Kansas. Springer has made this material the subject 

 of an elaborate monograph, and most of the great museums of the world con- 

 tain beautiful specimens from the now famous locality in Kansas. 



The asteroids contain representatives of both the Ophiuridse and the Stel- 

 lerida?, the genera Ophioglypha, Astropeeten, Goniaster, Pentagonaster, and 

 Pentaceros being found. The material comes from widely separated areas in 

 New Jersey, Texas, and Wyoming. 



The echinoids are very numerous, both the regular and irregular types being 

 well represented. The Lower Cretaceous deposits of Texas contain vast num- 

 bers of individuals at several horizons and in certain areas, while the Upper 

 Cretaceous of the Atlantic and eastern Gulf coasts, particularly in New Jersey, 

 North Carolina, Alabama, and Mississippi, although less fully characterized 

 by its echinoid fauna, affords many forms. The western Interior and Pacific 

 Coast Cretaceous contains a much smaller representation of echinoid types. 



Among the Lower Cretaceous genera found represented more particularly in 

 Texas are: Cidaris, Leiocidaris, Salenia, Hypodiadema, Goniopygus, Pseudo- 

 diadema, Diplopodia, Heterodiadema, Cottaldia, Pedinopsis, Orthopsis, Cyplio- 

 soma, Micropsis, Holectypus, Pyrina, Ananchytes, Holaster, Enallaster, and 

 Hemiaster, the last furnishing many species. Outside of Texas very few Lower 

 Cretaceous echinoids have been recognized, the Horsetown beds of California 

 containing a few forms. 



The Upper Cretaceous of the Atlantic and Gulf coasts has afforded repre- 

 sentatives of the following genera: Cidaris, Ualcnia, Pseudodiadcma, Copto- 

 soma, Psammechinus, Echinobrissus, Trematopygus, Botriopygus, Cassidulus 

 (many species of which have been recognized), Catopygus, Echinanthus, 

 Ananchytes, Cardiaster, Hemiaster, and Lintliia. Much the larger number of 

 forms have been found in the New Jersey Cretaceous, especially the Vincen- 

 town limesand bed of the Rancocas formation, which is regarded as probably 

 of Danian age. The western Interior and Pacific Coast areas contain few 

 representatives of the echinoids, most of the species belonging to the genus 

 Hemiaster. 



The Eocene deposits have afforded a considerable number of echinoderms, 

 but they are less numerous than in the Cretaceous. They are found at various 

 Eocene horizons on the Atlantic and Pacific coasts, but are most numerous 

 and characteristic in the South Atlantic and Gulf Eocene, where they occur in 

 large numbers. Nearly all of the echinoderm materials belong to the group of 

 the echinoids, although representatives of the Crinoidea, Asteroidea, and 

 Holothuroidea have been found. Among the echinoid genera recognized are 

 Cidaris, Ccelopleurus, Echinocyamus, Sismondia, Scutella, Mortonia, Breynella, 

 Echinolampas, Clypeaster, Cassidulus, Hemipatagus, Brissopsis, Ditremaster, 

 Lintliia, Schizaster, Eupatagus, Macropneustes, Sarsella. 



The Oligocene strata of the South Atlantic and Gulf areas have not been In 

 many instances satisfactorily delimited from the Eocene, so that the age of 

 LXIV — Bull. Geol. Soc. Am., Vol. 20, 1908 



