106 FOSSIL ASTEROIDEA. 



3. Ofhiotit.o^os MAGNUS, 11. sp. PI. XXVIII, figs. 5, 5 rt ; PI. XXIX, fig. 13. 



Specific Characters. — Proximal upper arm-plates broader than long. Spines 

 very short, seven spines on each arm-segment. Disc, with the exception of the 

 radial plates, covered with an extensive granulation. 



Material. — There are several sjiecimens Ijelonging to this species in the British 

 ]\Iuseuni (Nat. Hist.) and in the Sedgwick Museum at Camliridge. The specimens 

 in the British Museum bear the registered numbers E. 50G0 (Capron Coll.), E. 5050, 

 E. 370, and E. 371 (all from J. Starkie Gardner Coll.). The first-named speci- 

 men, which shows the ventral aspect, is figured on PI. XXVIII as the type. A 

 specimen from the Sedgwick Museum showing the dorsal aspect is figured on PI. 

 XXIX. 



Description. — This species is the largest of all the known Chalk Ophiuroids, the 

 diameter of the disc being about 37 mm., and the breadth of the arm at the base 

 5 mm. There appear to have been two tentacle-scales. 



Beuiarl-s. — Portions of the arm of this species are very similar in form to those 

 of Ojihiura serrata. Unless the disc is present it is difficult to separate this 

 species from that form. 



Localiti/ and Stratiijraphical Position. — Lower Chalk. 



<SH.6-orcZer— XECTOPHIUR^. 



Spines situated at an angle to the arm. 



F.n/H7//— AMPHIURID^, Ljungman, 1867. 



Zygophiurje with oral papillae from one to five, of which the last is generally 

 infradental. Arms inserted on ventral side of disc. Dental papillae absent. 



6'eH,HS— AMPHITJRA, Forhes, 1842. 



Disc small, delicate, covered witli naked overlapping scales, and furnished 

 with uncovered radial sliiclds. Teeth. Mouth-angles small and narrow. Arms 

 long, slender, even, and nunv or less flattened. Arm-spines short and regidar. 



