12 BRITISH PAL;EOZOIC PHYLLOCARIDA. 



of the valves has a linear ornament, and the ventral margin has a thin raised rim, 

 furnished, in some instances, -with small tubercles or a fine spinose fringe. 



Respecting the abdominal appendages which Mr. R. Etheridge, jun., described 

 in Appendix III of the ' Memoirs Geol. Siu'vey Scotland, Explanation of Sheet 

 23,' 1873, p. 93, he there remarks : 



" A further advance in the structure of this genus of Crustacea has been 

 satisfactorily established from specimens obtained at Lesmahagow by the Collector 

 of the Greological Survey, viz. the presence of respiratory locomotive appendages. 

 On a slab of thin-bedded shale are exposed the abdominal segments, telson, and 

 caudal appendages of a Ceratlocaris. From the ventral margin of the terminal 

 segment, to which are attached the telson-spines (Leptocheles, M'Coy), proceeds a 

 broad, paddle-shaped, membranous (?) expansion, presenting a strong marginal 

 outline, with a transversely striated surface. This is followed by another similar 

 appendage, proceeding in the same manner from the penultimate segment (somite). 

 Along the dorsal margin there is seen what appears to be the remains of one of 

 the corresponding ' foot-gills,' on the other side, bent back upon itself, and thus 

 thrust out of place. The free ends of these foot-gills are attenuated to more or 

 less rounded points. They do not show any evidence of having possessed a 

 marginal fringe. The discovery of these branchial locomotive appendages tends 

 to ally Geratiocaris still further with the genus Nebalia. See ' Geol. Mag.,' vol. ix, 

 p. 564. Loc. : No. 292 (Linburn or Linn Burn, about two miles north of Muir- 

 kirk, Lanarkshire). In thin-bedded shale (Upper Ludlow). Collected by 

 A. Macconochie." 



Fig. 1. Pig. 2. 



Fig. 1. — Abdominal segments and caudal spines of Ceratiocaris stygia, with indications of branchial laiuellsB or 



uropods, Geol. Surv. Mus. Edin., M. 101, Linburn. 

 Fig. 2. — Abdominal segments and caudal spines of Ceratiocaris papilio, with indications of uropod, Geol. Surv. 



Mus. Edinb., M. 94, Linburn 



Mr. R. Etheridge, jun., again alludes to this interesting subject in the ' Annals 

 and Mag. Nat. Hist.' ser. 4, vol. xiv, 1874, p. 9. 



Some of the abdominal segments seem to exhibit joint-marks or surfaces of 

 articulation adapted for appendages rather than for union with the next somite. 

 Compare PL III, fig. 3. 



Geratiocaris leptodactylus (M'Coy) and G. Murchisoni (Agassiz), having been 

 the first recorded species, will be here described first. 



