328 



MR. CYRIL CROSSLAXD ON THE 



[Feb. 16, 



first region, which narrows slightly to its posterior end, and the 

 rest of the body I'etains this slightly decreased breadth to near 

 the anvis. The figure of the worm (PI. XXII. fig. 10) gives these 

 |)roportions and illustiutes the difiei-ences between the two parts 

 of the body. As here shown, the change is quite sudden at the 

 point given. 



The prostomium (PI. XXII. fig. 10) is nearly as broad as the 

 liuccal segment and slightly notched anteriorly in the usual way. 

 The tentacles are smooth, short and thick, the longest projecting 

 but very little beyond the edge of the prostomium. The eyes are 

 large and densely black, of a half-moon shape, or slightly crescentic 

 from some points of view. The tentacular ciiri are remarkably 

 small and slender. 



The uppei- jaw-plates are of the usual type, the only noticeable 

 features being the bluntness of the teeth and the length of the 

 suppoiiis at the base of the great dental plates. As would be 

 expected fi-oui the small size of the worm, the plates are delicate 

 and of a liiiht brown colour, but calcareous matter is not visible. 



Upper and lower jaw-plates of Nicidion gracilis. X 60. 



There are two black crescentic paragnaths, one on either side 

 above and exterior to the crescent plates. The loAver jaws can 

 scarcely be called plates, they are so delicate and flexible. The 

 shapes of all these parts are shown in text-fig. 65. 



