221 
describe more fully, for a specific diagnosis, but comparison may be made 
with the Devonian Murchisonia anglica, d’Orbigny 1 , to which it seems to 
show most affinity. 
Trilobita. 
The slide No. 1354, Plate XXXVI., Fig. 13, shows a section of a 
trilobite carapace, attached to which is part of an appendage. It lies on 
the outer and ventral side, and resembles the so-called hydrospires of 
Cheirurus and allied forms. This peculiar and interesting structure con¬ 
sists of about 33 curved and flexuous processes emanating from a shelly 
layer attached to the ventral surface of the trilobite test, the curvature of 
the teeth-like process being so great as to cause the series to simulate a 
tube. On a detached portion of the same carapace, lying to 
one side are the remnants of three other quasi-spiral appendages, 
these latter terminating in a conical point. The structures seem 
to be comparable with the “ branchiae ” in Ceraurus and Calymene , from 
the Trenton limestone, figured by C. D. Walcott 2 . In all probability 
they are homologous with parts of the exopodites seen in other genera. 
The only trilobite occurring in the Buchan limestone, so far as I have seen, 
is a Cheirurus , collected by the late James Stirling, F.G.S., and it is signifi¬ 
cant that similar structures to that now figured are met with in this and 
related genera. 
Ostracoda. 
Primitia cuneus , sp. nov. Plate XXXVI., Figs. 10-12. 
Description. —Carapace seen from the side, broadly ovate; dorsal 
edge nearly straight, ventral, convex; anterior margin roundly truncate at 
the antero-ventral angle : posterior margin broad and bluntly rounded. 
Edge view, long-ovate, sub-acute anteriorly, swollen at posterior end. The 
median region of the dorsal area of the valves carries a slight depression, 
representing the median sulcus; whilst below, at the middle line and near 
the anterior, is a small pit or median depression. Surface of valves 
relieved by faint areolations, as in P. nitida. Roemer sp. 
Two specimens from No. 1018, one of which is figured as the holo- 
type. 
Measurements. —Dimensions of figured specimen.—Length of carapace, 
0.96 mm. ; height, 0.76 mm. ; thickness, 0.41 mm. 
A ffinities. —The above specimens are somewhat allied to F. A. Roemer A 
Primitia nitida 3 , which according to Prof. Rupert Jones, possesses features 
which “are liable to much modification” 4 . However, the sulcus and 
median pit in the Buchan species are not nearly so distinct as in P . nitida. 
in which features it more nearly approaches P. mundula , Jones 5 , as well 
as in its more distinct marginal rim. A. mundula , it may be remarked, is 
an Upper Silurian and Lower Devonian form. 
1. Prodrome, vol. I., 1849, p. 76. Pleurotomaria angulata, Phillips sp. Sandberger, 1856, Verst 
rhein. Schichtensyst. Nassau, p. 204, pi. XXIV., Fig*. 19. Murchisonia anglica , d’Orbigny, Whidborne 
1896, Pal. Soc. Lond., Mem. Dev. Fauna of S. of England, vol. III., pt. I., p. £9, pi. VI., Fig'. 14. 
2. Bull. Mus. Comp. Zool., vol. VIII., No. 10, 1881, pp. 220, 221, pi. III., especially’figs. 6 and 9. 
3. Cypridina nitida, F. A. Roemer, Palreontographica, vol. III., pt. II., 1852, p. 28, id. IV.,figs. 20, a,'b. 
4. Ann. and Mag. Nat. Hist. Pal. Bivalved Entom., No. XXXI. Some Devonian Species, vol. XV. 
ser. 6,1895, p 62. 
5 Jones. Ann. and Mag. Nat. Hist., vol. III., sev. 6, 1889, p. 376. 
