34 BRITISH PALEOZOIC PHYLLOCARIDA. 



the hollow or socket of an articulation in the larger caudal spine lying closely above 

 it, to have been a lateral or stylet. If so, its length (7| inches, though imperfect) 

 indicates a very great size for the whole animal, since the median or chief caudal 

 spine (style or telson) must have been much longer. Its relative position at 

 present can be accounted for by supposing it to have been pressed obliquely 

 outwards, so as to have been displaced backward. 



At f a piece of a caudal spine is seen separate from, and at a different level 

 from that of e, but showing obscurely the same kind of lumpy surface as at c, o ; 

 and higher up with a few obscure, minute, oval areoles with central pimples, or 

 prominences for the attachment of prickles. 



At G is the badly preserved upper end (If inch) of a caudal spine (probably 

 the telson or style) distinct from and at a different level to the others (e and r). 

 It is broader than either of the other two. Its proximal end widens out (^ inch) 

 before it is damaged and broken through, and thereby divided from what may be 

 its top portion, which is in apposition (with a joint) to the ultimate segment. It 

 retains (below the fracture) the curved socket for one of the laterals or stylets. 



Unfortunately, nothing of the other extremity of this large spine (g) is to be 

 seen in the further part of the stone. 



PI. IX, figs, la, 16. Geratiocaris Ludensis, H. "W., as in PI. I, but not 

 reduced. 



Fig. 1 a. The impression of the penultimate and ultimate segments in the 

 matrix, and the caudal appendages, all of the natural size. The former show the 

 impressions of the raised wrinklets on the matrix, and some portions of the inside 

 of the test with its sunken striee, or backs of the wrinklets ; also the articulation 

 (somewhat crushed) of the head of the telson, and below, broken off, the remnants of 

 the three large caudal spines, figured two thirds natural size in PI. I, and described 

 at p. 33. The outer (right hand) seems, at first glance, to be the style, but very 

 possibly the inner one (on left hand), though not in its natural position, may have 

 been really the large, median spine or telson. The articulation above probably 

 belonged to it ; especially as a socket under its shoulder seems to be fitted by the 

 head of the outer spine. This latter, and the more obscure third spine, may well 

 have been the lateral spines thrown out of position by pressure. 



Under these circumstances the length of the main caudal appendage (telson or 

 style) cannot be ascertained, and it may have been at least more than half as long 

 again as the lateral spine, which measures 7f inches. 



Fig. 1 b. The lower portion of the spine marked c, enlarged twice. (See also 

 PI. I, c) 



