GX SLL) 
XXI.— Further Researches among the Crustacea and Arachnida of the Car- 
boniferous Rocks of the Scottish Border. By B. N. PrEacu, A.R.S.M., 
F.R.S.E., of the Geological Survey of Scotland. (Plates XXVIII. and 
SX.) 
(Read 20th March 1882.) 
I have again been privileged by Professor A. GErk1E, Director-General of 
the Geological Survey of Great Britain and Ireland, in being allowed to bring 
before this Society the results of a further study of the Crustacea and Arachnida 
obtained by the Geological Survey from the Lower Carboniferous rocks of the 
Scottish Border. Since my former papers on those subjects were read, a con- 
siderable amount of fresh material has come to light, which has allowed of 
many species, which were formerly represented by fragmentary specimens, to be 
more fully described, and several altogether new to science to be added to our 
former list. 
Class I. CRUSTACEA. 
The Crustacea, as formerly, arrange themselves under the orders Phylopoda 
and Decapoda. 
Order I. PHYLLOPODA. 
In my former paper I described two species of Phyllopoda, which I referred 
to the genus Ceratiocaris, Salter. Since then I have been enabled to study a 
large suite of these fossils belonging to at least three species, and I now 
think that, though they are very nearly allied to Ceratiocaris, they differ so 
much from it as to warrant their being erected into a separate genus, for which 
I propose the name of Acanthocaris, or spine-shrimp, from the spine-like telson. 
Acanthocaris, gen. nov. 
Characters.—Carapace small, and not hinged, produced anteriorly into a 
blunt snout, and posteriorly into rounded lobes. Body fusiform and long, com- 
posed of numerous segments which increase in length backwards, the seven 
posterior ones being uncovered by the carapace. Third segment from tail 
tumid, and notched on its ventral surface. Telson long and spiniform, and 
flanked on each side by a rudimentary spinelet. Test smooth or slightly 
wrinkled, but not striated longitudinally. 
VOL. XXX. PART II. 41 
