271 



On NECROGAMMARUS SALWEYI, (H. Woodward) an am- 



PHIPODOUS CRUSTACEAN FROM THE LOWER LUDLOW OF LEINT- 

 WARDINE. 



BY HENKY WOODWAKD, F.G.S., F.Z.S., &c. 



Whilst visiting Ludlow and its Museums last year, I had the opportunity 

 to examine the very interesting Crustacean fragment preserved in the cabinet of 

 Mr. Humphrey Salwey, of the Cliff, Ludlow, which was noticed and figured in 

 Messrs. Huxley and Salter's important work on the Eurypteridce (Memoirs of 

 the Geological Survey, Monograph I., 1859, p. 25, pi. XIII., Fig. 7.) Prof. 

 Huxley observes, " The fossil figured is evidently Crustacean, but it exhibits no 

 character by which it can be identified as a part of a Pterygotus." (See Fossil 

 Sketches, No. 11, Fig. 2.) 



It differs from Prcearcturus gigas, inasmuch as it presents us with the 

 side-view or profile, of what appear to be three laterally-compressed and thin- 

 crusted somites or body-rings, whereas in Prcearcturus we see the full ventral 

 and dorsal aspect of a thick, flattened, but slightly-arched segment without 

 epimera. The feet also in P. gigas take their rise along the centre of the sternum, 

 whereas in this Ludlow fossil they are articulated along the border. The section 

 of the limbs is very different in the two forms. 



The first somite (a) measures 10 lines in greatest breadth and 2\ inches from 

 the dorsal line to its sharply-pointed epimeral border, at the anterior side of 

 which, at x, there appears to be the remains of the base of an appendage belonging 

 to a preceding somite not preserved. 



At the posterior side of the sharp epimeral border of this somite appears 

 the base of 'a limb (a 1) nearly square in section which most probably belonged 

 to the segment marked (a). 



The second somite (b) is 11 lines in breadth and If inches from the dorsal 

 line to the broad truncated border from which the appendage (b, 2) takes its 

 rise. A deep sulcus (s) passes over the dorsal line of this segment near the 

 middle marked by a depression on the side where it dies away. 



The third segment (c) is 10 lines broad and measures 2 inches from tha 

 dorsal line to the sharply-pointed epimeral border ; from the posterior side of 

 this the limb (c 3) is given off of which six joints are visible, the first or basal 



