ECHINODEKMATA. 171 



of Comatula, enjoys the faculty of locomotion. The Comatula and 

 Pentacrinus Caput- Medusae are the only living representatives of the 

 Order. The Cystids, as also the Blastoids — another little group of Pal- 

 aeozoic Echinoderms, — have been separated from the true Crinoids into 

 distinct Orders ; but we shall include them under this head. 



No. 864. Actinocrinus proboscidialis, Hall. 



The Actinocrinoids, found chiefly in the Carboniferous 

 limestone, are sometimes provided with thorn-like side arms 

 which project from the column at irregular distances. The recep- 

 tacle is of an irregular subspherical form, and frequently having 

 arms passing off at right angles like the spokes from the nave 

 of a wheel. This species is from the Burlington limestone 

 (Carboniferous),Burlington, Iowa. Price, $0.15. 



No. 865. Actinocrinus aequalis, Hall. 



From tha same formation and locality as the preceding. Price, $0.15. 



No. 866. Actinocrinus aeqmbrachiatus, McChesney. 



From the Burlington limestone (Carboniferous), Monmouth, 111. 



Price, $0.15. 



No. 867. Actinocrinus Agassizi, Troost. 



From the Keokuk limestone (Carboniferous), Crawfordville, Ind. 



Price, $0.30. 



No. 868. Actinocrinus althea, Hall. 



From the Burlington limestone (Carboniferous), Burlington, Iowa. 



Price, $0.25. 



No. 869. Actinocrinus biturbinatus, Hall. 



Body and arms. From the Keokuk limestone (Carboniferous) Crawford- 

 ville, Ind. Price, $0.25. 



No. 870. Actinocrinus cornigerus, Hall. 



From the Burlington limestone (Carboniferous), Burlington, Iowa. 



Price, $0.20. 



No. 871. Actinocrinus formosus, Hail. 



From the same formation and locality as the preceding. Price, $0.15. 



No. 872. Actinocrinus Fosteri, McChesney. 



From the same formation and locality as the preceding. Price, $0.15. 



No. 873. Actinocrinus G-ouldi, Hall. 



From the Keokuk limestone (Carboniferous) Warsaw, 111. Price, $0.30. 



