216 



ECHINODERMA TA. 



ORDER AGELACRINOIDEA. 



FAMILY AGELACRINID^E. Agelacrinus, Echinodiscus, Edrioaster, Lepidodiscua. 

 FAMILY HEMICYSTID^. Heraicystites. 



ORDER MYELODACTYLOIDEA. 

 FAMILY MYELODACTYLIDTE. Myelodactylus. 



ORDER CYCLOCYSTOIDEA. 

 FAMILY CTCLOCTSTOIDEDJB. Cyclocystoides. 



ORDER LICHENOCRINOIDEA. 

 FAMILY LICHENOORIN m JR. Ijichenocrinus. 



CLASS STELLERIDA. 

 ORDER ASTEROIDEA. 



FAMILY ONYCHASTERID^E. Oaychaster. 



FAMILY PAL^EASTERID^:. Cholaster, Compsaster, Palseaster, Palaeasterina, 

 Petraster, Schoenaster, Stenaster, Tremataster. 



ORDER OPHIUROIDEA. 

 FAMILY PROTASTERID^E. Eugaster, Palseocoma, Pro taster, Tseniaster. 



CLASS ECHINIDA. 

 ORDER PERISCHOECHINIDA. 



FAMILY ARCHJEOCIDARIDJE. Archseocidaris, Eocidaris, Lepidocidaris, Peris- 



chodomus, Pholidocidaris. 



FAMILY LEPIDECHINID^. Hybochinus, Lepidechinus. 

 FAMILY PAL^CHINIDJE. Lepidesthes, Melonites, Oligoporus, Palsechinus. 



ACROCRINUS, Yandell, 1855, Am. Jour. Sci. 

 and Arts, 2d ser., vol. 20, p. 135. [Ety. 

 akros, extreme, from the great number 

 of plates covering the body ; krinon, 

 lily.] Body goblet or urn-shaped, con- 

 sisting of many series of plates ; two 

 basals, the suture from the anterior to 

 the posterior side, followed by a series 

 of small plates, and these again by 

 another and another, so that the plates 

 reach the 5th to 10th series before the 

 arms become free ; the size of the plates 

 increase as they approach the arms ; 

 arms 20, long, composed of two series 

 of plates bearing pinnules ; column 

 round. Type A. shumardi. 



ghumardi, Yandell, 1855, Am. Jour. Sci. 

 and Arts, 2d ser., vol. 20, p. 135, Kas- 

 kaskia Gr. 



urniformis, Hall, 1858, Geo. Rep. Iowa, p. 

 690, Kaskaskia Gr. 



wortheni, Wachsmuth, 1882, Bull. No. 1, 

 111. St. Mus. Nat. Hist., p. 4, and Geo. 

 Sur. 111., vol. 7, p. 343, Coal Meas. 

 ACTINOCRINUS, Miller, 1821, Nat. Hist. 

 Crinoidea, p. 95. [Ety. aktin, ray ; 

 krinon, lily.] Body turbinate, plates 

 sculptured; basals 3; primary radials 

 3x5; secondary 1 x 10, axillary ; suc- 

 ceeding radials having a single series 

 to each division, one axillary, the other 

 simple; arms 20 to 50 or more; pin- 

 nules ; regular interradials, one in the 

 first series, two in the second, and one 

 or two in the third ; azygous inter- 

 radials, one in line with the first 

 primary radials, and pi the same size, 

 two in the second series, and one, two, 

 or three in succeeding series; vault 

 variable, plates nodose; tube or pro- 

 boscis large, subcentral ; column long. 

 Type A. triacontadactylus. 



