T H E ANNALS 



AND 



MAGAZINE OF NATURAL HISTORY. 



[THIRD SERIES.] 

 No. 27. MARCH 1860, 



XV. On new Fossil Crustacea from the Silurian Rocks. 

 By J. W. SALTER, F.G.S., A.L.S. 



THE Phyllopod group, rather poorly represented in modern seas, 

 was rich in species and genera in palaeozoic times, if we are cor- 

 rect in referring to it the numerous bivalved and Apus-like forms 

 in mountain limestone and the Silurian strata. The species 

 were of large size, too, compared with living members of the 

 group the bivalved forms generally larger than Estheria, and 

 (if, as is most probable, the great Posidonia from the Carboni- 

 ferous rocks be truly Crustacean) far larger even than Limnadia. 

 Numerous smaller species accompany these, of a great variety of 

 forms ; and these are only now beginning to be made known by 

 Mr. Rupert Jones and M. Barrande. 



Of the forms like Apus less is known ; but the Dithyrocaris 

 of the Scotch coal-shales is pretty generally allowed to be a 

 great Phyllopod, with a carapace not more bent than that of 

 Apus, if so much so. 



Ceratiocaris, a Silurian fossil, of equal size, was first described 

 by Professor M'Coy in the ( Annals Nat. Hist.' vol. iv. p. 412 ; 

 and some details were filled up by myself in the ' Quarterly Geol. 

 Journal' for 1856, vol. xii. p. 33. At the time that Prof. M'Coy 

 wrote, only half carapaces were known, and the relations of the 

 animal could not be very clearly made out ; but the mucronate 

 anterior and truncate posterior margin, and the fine longitudinal 

 sculpture were figured by him, as well as an anterior tubercle, 

 which he regarded as an eye-spot, but which proves to be the 

 impression of the hard mandibles pressed through the crust. 

 Good specimens were afterwards found in the south of Scotland, 

 at Lesmahago, Lanark, a spot now famous for its rich fossil beds ; 

 and these showed the body-rings, telson, and lateral appendages. 

 The appendages had been long known, in a disjointed form, as 

 Leptocheles, M'Coy. A restored diagram of the animal was given 



Ann. fy Mag. N. Hist. Ser. 3. VoLv. 11 



