8 BRITISH PALAZOZOIC FOSSILS. [Zoopuyra. 
DIPLOGRAPSUS PRISTIS (/is. Sp.) 
Syn. and Ref—Prionotus pristis. His. Leth. Suec. t. 35. f. 5. 
Sp. Ch.—Straight, simple, about two inches long, and one line wide, gradually tapering to the base ; 
central axis capillary, the dissepiments diverging from it at an acute angle, their upper and lower margins 
parallel, forming narrow cylindrical tubes, when uncompressed, with the opening simply truncate at the outer 
end; when compressed, the walls of the cells form parallel lines very oblique to the axis, producing denti- 
cles at the edge, with a long straight lower, and a very short concave upper, margin; five in the space of 
two lines. 
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This probably distinct species accompanies the above in the Utica slate of New York, and also rarely 
at Lockerby ; it seems distinct from the true pristis by its broader, triangular teeth, slightly mucronate at 
the tip, and cells much less oblique to the axis; it is more strongly and broadly toothed than the D. mucronatus. 
Position and Locality—Common in the shale, three miles North of Builth; at Pen Cerrig; Lockerby, 
Dumfriesshire ; Llansantfraid Slate-quarries, Denbighshire; a small doubtful fragment in the fine Caradoc 
sand-stone of the Hollies, Church Stretton, Shropshire. 
DipLograpsus rAMosus (Hall. Sp.) 
Syn. and Ref—Graptolites ramosus. Hall. (Pal. N. Y. t. 78. f. 3.) 
Sp. Ch.—Polypidom several inches long, slender, two-thirds of a line wide, bifurcating at an angle of 
45°; main stem with cell-denticles on both margins, branches with them only on the outer margin, the 
inner margin straight, smooth, and thickened; denticles scarcely five in the space of two lines, narrow, only 
slightly inclined to the axis, obtuse at the extremity, upper and lower margins sub-parallel, the wide space 
between each denticle with a straight edge parallel with the axis. 
The small size, remoteness, and peculiar form of the denticles, distinguish to the careful observer the 
main stem from the D. pristis, and the branch from the G. Sagittarius. 
Position and Locality—Only one specimen of this very distinct species has occurred to us, in a 
decomposing bit of shale from an old slate-quarry between Ulverstone and Ireleth. Hall’s specimens were 
from the ‘ Utica slate,” near Albany; and this specimen, therefore, seems to connect the bed in which it 
oceurs with the glazed slates of Cairn Ryan, in Scotland, where most of the other Utica slate Grapto- 
lites are found. 
DIPLOGRAPSUS RECTANGULARIS (M/°Coy). Pl. 1. B. fig. 8. 
Ref —M°Coy. Annals Nat. Hist. 2nd S. Vol. VI. p. 271. 
Sp. Ch.—Straight, simple, usually from one to one and a half inches long, one line wide, gradually 
tapering to the base, which is a fine simple point; axis fine, capillary; cells perfectly at right angles to 
the axis, forming square denticles to the margin, distinctly separated by rather wide parallel-sided notches, 
reaching two-thirds of the way to the axis; five in the space of two lines. 
This species is more distinct and constant in its characters than most of the allied forms ; in general 
appearance it approaches the D. pristis (His. Sp.), but is easily distinguished by the short square cells, 
set at right angles to the axis, instead of the narrow very oblique ones of that species. The only Graptolite 
making any approach in the form and direction of the denticles is the dicornis of Hall, which, however, 
is distinguished by the strong, lunate process to the base from which it derives its name—the base of the 
present species being a simple point, as in the D. pristis. There is also in most of Mrs Hall’s figures a per- 
ceptible obliquity in the denticles, which so admirable an artist could not have designed for this species: the 
bicornute base (so commonly preserved in the D. dicornis) certainly does not appear in ours. Both this and 
the D. pristis being of considerable thickness are occasionally liable to be compressed in a plane at right 
