OPHIURA PARVJSENTUM. 103 



vascular canal and for the nerve-ring ; and the depressions for the first mouth- 

 tentacle and the entrance to the branch of the water vascular system are clearly 

 shown. Fragments of the scaly covering of the disc are seen scattered over the 

 disc. The peristomial plates are not recognisable, as is also the case in modern 

 species of Ophiura. The arms are 3 mm. wide at the base. The upper arm-plates 

 near the disc are broad. Six (or seven ?) spines, which are in length about a 

 third of the length of the arm-segment, are present. 



The vertebral ossicles are figured on PI. XXVII, figs. 3 c, 3 d, 3 e. They show 

 the typical Ophiurid structure as displayed by modern species of Zygophiurids. 



Locality and Stratigrapliical Position. — Upper Chalk, Bromley, Kent. 



2. Ophiura Fitchit, n. sp., ex Forbes, MS. PI. XXVII, figs. 2, 2 a, 2 b. 



Specific Characters. — Body large and stoutly built. Disc covered with large 

 swollen plates. Radials contiguous, large, kidney-shaped. Upper and lower arm- 

 plates small. 



Material. — An external cast in flint, the sole remains of this species, is 

 preserved in the Norwich Museum (No. 2294). 



Description. — Very little can be made out concerning the structure of this 

 ophiurid. The disc appears to have been surrounded with a circlet of large 

 radials. It has a diameter of about 16 mm. 



A plasticine mould of the lower portion of the cast is figured on PI. XXVII, 

 fig. 2o. The jaws (oral angle plates) are distinctly seen. They were long and 

 slender, and similar in form to those of 0. serrata. Similarly a peristomial plate is 

 not visible. The inter-radial rounded buccal shield is clearly seen. The arm is 

 4 - 5 mm. broad at the base. The impression of the cast of the arm appears to 

 indicate that both upper and lower arm-plates were small, as the side arm-plates 

 appear to meet in the dorsal and ventral median lines. 



Locality and Stratigrapliical Position. — From flint gravel, Mousehold, Norwich. 



3. Ophiuka parvisentum, n. sp. PI. XXVII, figs. 4, 4 a. 



Specific Characters. — Disc covered with small plates, radials inconspicuous. 

 Proximal upper arm-plates only occupying about one third of dorsal surface of 

 arm. Five spines on each side of arm-segment. 



