18 BRITISH PALAEOZOIC PH YLLOCARIDA. 



G. Murchisoni, founded on the specimens figured in ' Sil. Syst.' and ' Siluria,' but 

 now unfortunately mislaid, is represented by several analogous fossils, such as 

 Oxford Museum B and C ; Ludlow Museum C ; M. P. G. |f and f f , ,. We find 

 only one row of pits on the styles, as exposed. We have been unable to determine 

 its carapace. The carapaces assigned by Salter to G. leptodactylus and G. Murchi- 

 soni arc not accepted by us. We formerly thought that they belonged to one 

 species, but now regard them as distinct. 



Several good examples of more or less perfect sets of three caudal spines, corre- 

 sponding in size, strength, curvature, and ribbing -with Murchison's fossils, have 

 been met with. Some of these show evidence of lines of prickles (by the presence 

 of little pits, representing their bases), and on close examination the engravings in 

 the ' Sil. Syst.' and ' Siluria ' (the specimens have been mislaid) show some slight 

 indications of this spinose ornament. 



We have not found a carapace directly associated with any tail-spines of 

 either the Ahirchisoni or the lepfodacfylas type. With regard to both however, the 

 late Mr. J. W. Salter satisfied himself that he knew their special carapaces, for he 

 described them at p. 157 of the ' Ann. Mag. Nat. Hist.' for March, 1860, where 

 also he refers both species to the Geratiocaris of M'Coy. Judging from his Latin 

 diagnoses, he allocates to the former " a cephalothorax (carapace) two inches long, 

 oblong, convex, ornamented with interrupted, nearly straight, wide-apart lines. 

 The caudal appendages long, sub-cylindrical ; the central spine (telson) strong, 

 bulbous at its base, and with a strong dorsal rib ; the side spines long. All ribbed. 

 The whole animal medium-sized. Specimens possessed by the geologists at Ludlow 

 and by the Museum of Practical Geology." The carapace described here does not 

 agree with any that we can associate with the caudal spines intended. 



PI. Ill, fig. 4 a. Four body-segments with outside test, and impressed caudal 

 spines. Ornamentation consisting of longitudinal, abrupt, delicate wrinklets ; and 

 on the head of the crushed telson strong leaf -like anastomosing lines. Fig. 4 b. 

 A segment, magnified, showing the ornament. 



Mus. Pract. Geol. ; one of those marked " ff . G. tyrannus, Salter." ' Catal.,' 

 1878, p. 118. Leintwardine. In brownish-grey mudstone. 



PI. Ill, fig. 7. Two stylets, irregularly rugose (probably decomposed). Mus. 

 Pract. Geol. " f|. Wyatt-Edgell Collection, 1878. Lower Ludlow; Leint- 

 wardine. Geratiocaris Miirchisoni, M'Coy." See ' Catal.,' p. 118. In darkish 

 olive-grey micaceous mudstone. 



PI. IV, fig. 1. Head of telson leaf -marked, crushed; top of stylet with 

 rounded head, in place : the rugosities on the stylets are probably due to decom- 

 position. There are some regular pittings on the style (=4 inches = 105 mm.), 

 which is ridged, as also are the stylets. Oxford Museum B. In brownish-grey 

 mudstone ; Lower Ludlow. Marked *' Murchisoni." 



