OPHIURA. 101 



Description. — The disc is small and very much distorted. The ventral 

 aspect of one arm is the only portion of the star-fish which affords much 

 opportunity for description. The arm is about 18 mm. long and 4 mm. broad, 

 and possesses the cylindrical characteristic shape of the genus. It is composed 

 of a large number of square ossicles, which are superposed in the cross-section of 

 the arm, so far as it can be seen. They possess no spines, but a regular granula- 

 tion appears to run lineally across their breadth. 



Remarks. — This specimen is not sufficiently well preserved to ascribe it to a 

 definite species of the genus. 



Stratigraphical Position. — Lower Chalk. 



CRETACEOUS OPHIUROIDEA. 



Order— ZYGOPHIUILE, Bell (1892). 



Ophiuroidea, in which the movement of the ossicles on one another is limited 

 by the development of lateral processes and pits. Superior, inferior, and lateral 

 spine-bearing arm-plates are always present. The arms are simple and cannot 

 coil round straight rods. 



Family— OPHIOLEPIDIDvE. 



Zygophiurae with oral papillae from three to six, of which the last may be 

 infradental. Arm incisures on the disc. Dental papillae absent. 



£ e7ms — OPHIURA, Lamard; 1801. 



Ophiura, Lamarck. Histoire Naturelle des Aniinaux saus Vertebres, vol. ii. 



Ophiolepis, Milller and Troschel, 1842. System der Asterideu (Braunschweig). 

 Ophiogltpha, Lyman, 1865. (Ophiuridse and Astrophytidse) 111. Cat. Mus. Comp. 



Zool. Harvard, Nos. i, viii ; 1882, Rep. Challenger Zool., 



vol. V. 

 Verrill, 1899. Report on the Ophiuroidea collected by the Bahama 



Expedition in 1893 ; Iowa City, Bull. Labor. Nat. Hist., p. 4. 



Disc covered with plates or scales which are for the most part swollen. 

 Eadial shields naked and swollen. Teeth. The inner mouth-papillae long but 



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