OPHIOTITANOS L^VIS. 105 



is a large number of granules in the oral region, but the tips of the jaws (oral 

 angle plates) can be seen just above the mouth-shields. There appear to be five 

 (or six) squarish mouth-papillse. 



The first under arm-plate is small and with rounded edges. Distally the 

 under arm-plates are at first almost square, then roughly pentagonal, and finally 

 triangular, with the apex pointing towards the disc. The side arm-plates meet 

 below at about the seventeenth arm-plate. The upper arm-plates are at first 

 hexagonal, but rapidly become roughly triangular. They are tumid in appearance 

 and have a rounded base. They rapidly become smaller, and allow the arm-plates 

 to meet dorsally. 



There are on each arm-segment five small smooth spines considerably shorter 

 than the length of a segment. 



There appear to be two tentacle-scales, but the exact number is rather 

 difficult to determine. 



Locality and Stratigraphical Position. — Lower Chalk, Folkestone and Dover. 



2. Ophiotitanos l^ivis, n. sp. PL XXVIII, figs. 3, 3 a, 4, 4 a. 



Specific Characters. — Spines longer than arm-segments. Upper arm-plates 

 broader than long. Plates of dorsal surface of disc not hidden by granules. 



Material. — Only one specimen is known. This is preserved in the British 

 Museum (Nat. Hist.), no. E. 5053 (purchased of Mr. Griffiths), and shows the 

 dorsal aspect. 



Description. — The diameter of the disc is 48 mm., being thus about the same 

 size as Opltiotitanos tenuis. The arm is, however, not so broad at the base, 

 measuring here only 1*5 mm. across. The specific characters given above 

 separate it sharply from this last-named species. I have not been able to 

 determine the number of spines on each arm-segment. 



Locality and Stratigraphical Position. — Lower Chalk, Dover. 



Remarks. — A small specimen upon the slab, no. E. 5058 (PI. XXVIII, figs. 4, 

 4ft), may be a young member of this species, as it possesses a strong general 

 resemblance to the above. It is peculiar in having only four arms, probably an 

 abnormality. As explained on p. Ill, Ophioglypha bridgerensis, Meek, is very 

 similar in appearance to this species. 



