466 R. ETHERIDGE ON THE GENUS DITHYROCARIS 
specimen are the remains of the slightly rounded posterior margin 
which connects the median ridge of the carapace with the posterior 
lateral spines on each side. In the figure the two halves of the 
carapace have been placed in apposition, to show their relation to 
one another, the dotted portions being restored. 
Loc. and Horizon. Tweeden Burn, near junction with Liddel 
Water, by New Castleton, Roxburghshire; in the Cement-stone 
group of the Calciferous Sandstone series. 
Coll. Geol. Survey of Scotland. 
Collector. Mr. A. Macconochie. 
DiTHYROCARIS TRICORNIS, Scouler. 
Argas tricornis, Scouler, Records of Gen. Science 1835, i. p. 136. 
Dithyrocaris tricornis, Morris, Cat. Brit. Foss. 2nd ed. 1854, 
p. 107; Salter & Woodward, Cat. & Chart of Foss. Crustacea, p. 17, 
f. 12; Woodward & Etheridge, Brit. Assoc. Report for 1873, 
pt. 2, p. 92; Mem. Geol. Survey Scotl. Expl. 23, 1873, p. 99 ; 
Geol. Mag. 1873, x. p. 483, t. 16. f. 2 & 3; Woodward, Cat. 
Brit. Foss. Crustacea, 1877, p. 73; Bigsby, Thes. Dev.-Carb. 1878, 
p. 249. 
Obs. To this species are referred portions of the two halves of a 
much larger carapace, disunited, but lying partially over one an- 
other. They both exhibit the strongly and obliquely striated lateral 
margins and the toothed or serrated lateral ridges, terminating in 
one of the strong recurved posterior spines. There is no trace of 
the fine ornamentation on the surface exhibited by the specimen 
discovered by Mr. James Bennie, now in the collection of the Geolo- 
gical Survey of Scotland, and figured by Dr. Woodward and myself. 
On the contrary, there is evidence of the peculiar striated lamina- 
tion so often found on the carapace-surface of D. testudineus, and 
seen also on the segments accompanying the specimen before men- 
tioned as found by Mr. Bennie *. 
To D. tricornis are also referred some strong and bold tail-spines. 
The side spines measure one inch two lines long, the central one 
being a trifle shorter. They are ornamented with the before-men- 
tioned laminar strie, directed longitudinally, with here and there 
Tugosities scattered over the surface. 
Loc. and Horizon. Liddel Water, half a mile below New Castle- 
ton; Tweeden Burn, near junction with Liddel Water, by New 
Castleton, Roxburghshire. Cement-stone group of the Calciferous 
Sandstone series. 
Coll. Geological Survey of Scotland. 
Collector. Mr. A. Macconochie. 
Diruyrocaris, sp. ind. (Pl. XXIII. figs. 2 & 3.) 
Obs. There are in the collection made by Mr. Macconochie four 
specimens, consisting of abdominal somites and tail-spines, which 
must haye belonged to aspecies fully as large as D. tricornis, Scouler. 
* Geol. Mag. x. t. 16. f. 3e. 
