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Locality and formation.—Mingan Islands, White Limestone.
Genus PILEOCERAS, (Salter.) Mr. Salter has informed me that he intends to describe under the above generic name some remarkable fossils that have been found at Durness in Sutherlandshire Scotland, where they occur associated with Ophileta compacta and others allied to species of the Calciferous Sandrock and Chazy limestone. A species of the same genus has been collected in this country, but lest any confusion should take place I shall not describe it until I can see Mr. Salter's paper.
Genus LITUITES ? There are two species apparently of this genus in the Calciferous Sandrock, but the specimens are so imperfect that they cannot be sufficiently characterised.
Genus BATHYURUS, (New genus.) Generic Characters. — Trilobites of a medium size, oblong oval ; head thorax and pygidium sub-equal ; facial suture in front of the eye nearly parallel with the longitudinal axis of the body, reaching the anterior margin and behind the eye dividing the posterior margin; glabella sub-clavate conical or cylindro-conical usually prominent and without lobes, but sometimes with several obscure lateral transverse sulci, divided behind by a neck furrow; hypostoma oblong not forked, somewhat oval, an elevated margin around the posterior two thirds in some of the species, muscular impressions two, transverse or oblique, situated behind the middle ; thorax in the species in which it has been observed with nine segments ; pleuræ grooved.
The above genus is proposed to include serveral species of Lower Silurian trilobites of which B. extans (Asaphus extans, Hall), may be regarded as the type. It should perhaps be consid. ered as a sub-genus of Asaphus of equal value with Megalaspis (Angelin) from which it differs in the form of the head and pygidium and in the number of the segments of the thorax. I shall give some further illustrations of the genus hereafter.
I have provisionally referred the following species to Bathyurus.
BATHYURUS AMPLIMARGINATUS, (N. s.)
Fig. 12, a, 6. Description.—The pygidium of this species is nearly semi-circular its length being only a little more than half its width ; the axis is elongate conical very prominent and distinctly defined all round, its length about two thirds, and its greatest width one fifth that of the whole pygidium ; it is crossed by five distinct transverse furrows but the terminal one third is either smooth or marked by extremely obscure sulci. On each side of the axis there are five ribs; the first of these is only partly preserved in the specimen, the second at about half its length contracts to one half its width and appears to become obsolete before reaching the margin; the third rib is in length equal to the width of the axis at the point where it is attached; the fourth a little shorter, while the fifth is simply a triangular convex space between the fourth furrow and the posterior third of the axis. The most striking character is the broad smooth margin, the width of which is about one fourth that of the whole pygidium.
Associated with this pygidium and in the same mass of stone was found the glabella represented by Fig. 12, a. It is depressed cylindro-conical, length eight lines, width four lines and a half, a strong neck segment one line and a half in width.
Locality and formation.—Mingan Islands, White limestone. Collectors.—Sir W. E. Logan. J. Richardson.
BATHYURUS CYBELE, (N. e)
Fig. 12, c. Description.–Of this species the glabella only has been found It is slightly clavate being a little wider near the front than it is at the neck furrow; it is convex, with an elevated rounded front; two obscure barely visible lateral sulci not reaching the centre; one of these furrows is at about one third the length from the neck furrow, and the other at two thirds ; they slope forward and outward at an angle of about 55° ; the neck furrow is deep concave, and with a forward sinus in the middle. The surface is covered with small tubercles. The front of the glabella is slightly produced into an obtuse scarcely visible, rounded lobe one third the whole width. Length nearly five lines, width four lines.
Locality and formation-Mingan Islands, White limestone. Collectors.--Sir W. E. Logan, J. Richardson.
BATHYURUS Conicus, (N. s.)
Fig. 12, d. Description.—Glabella conical rather strongly convex, with a deep neck furrow and a deep sulcus all round, covered with small sharp tubercles distant from one fifth to two fifths of a line from each other. In the specimen a small portion of the anterior margin of the cephalic shield in front of the glabella is preserved. It seems to shew that the whole head was surrounded by a deep marginal furrow. Length of glabella including neck segment five lines and a half; width at neck segment four lines. The most striking features are the regularly conical shape of the glabella and the tubercular surface. The margin in front of the glabella is two lines wide.
In the same rock and near the same locality, the cheek piece of a trilobite was found with a tubercular surface, and with the posterior angle produced into a short spine. It probably belongs to this species.
Locality and formation.—Near Beauharnois, Calciferous Sandrock. Collector.-J. Richardson.
ASAPHUS ? A single fragment of a large Asaphus was collected at the Mingin Islands in the Calciferous Sandrock.
LEPERDITIA ANNA, (Jones). L. ANNA, (Jones) Annals of Natural History, 3rd series, vol. 1,
p. 247, plate ix., fig. 18. – Canadian Fossils, Decade 3, p. 96, plate xi., fig. 13. This species has been found only at the original locality in a quarry near the Station House of the Grand Trunk Railway, St. Anns.
ARTICLE XXVIII.—Descriptions of some new species of Trilo
bites from the Lower and Middle Silurian rocks of Canada.
By E. BILLINGS. (Extracted from the Report of the Geological Survey of Canada for 1858
2.-Side view of same specimen.
3.-View of pygidium of the same. Description. Oblong, oval, distinctly trilobed, the central lobe very broad, full half the whole width. Length two to three inches, width half the length. Head rather more than one third, the thorax about one third and the pygidium rather less than one third the whole length.*
The head is large, very convex, most prominent in the centre and in form about one fifth more than the quarter of a sphere; the dorsal furrows continued on it about one third the length, subparallel, a little curved outwards at their anterior extremities distant from each other half the width of the whole head; cheek
* All the measurements of the head and pygidium given in this article (unless otherwise stated) were made by placing one point of the divi. ders at the centre of the anterior, and the other at the centre of the posterior margins. The figures would be different if the length were in all cases taken from the most forward projecting point, and this would be the proper mode, provided we knew how the animel carried its head.
pieces small, the facial suture half way between the dorsal furrow and the genal angle, eye rather small and situated about half its own length from the posterior margin; genal angles broadly rounded.
Thorax with ten segments, axis evenly convex, rather prominent, full half the whole width, about one sixth longer than wide, its sides nearly straight and the width at the first segment slightly greater than at the last; on each side of the axis a very narrow flat space scarcely one sixth the width of the axis, its outer margin forming the line of the fulcra of the pleuræ ; the pleuræ are in length equal to about half the width of the axis, at the fulcra they appear to be bent at an angle of about 45°. The segments of the thorax increase in width from behind forwards.
The pygidium is in the extent of its surface about half the size of the head, transversely oval but with its lateral extremities obli. quely and largely truncated, the posterior margin broadly and regularly rounded, the front margin trilobed, the central lobe being six eights of the whole width, the axis either not at all or only very obscurely defined.
The surface is smooth with the exception of the front part of the head which is marked by fine undulating concentric fissures about six in one line. The course of the facial suture has not been distinctly observed behind the eye.
Only one specimen with all the parts in place has been collected. It is rolled up and its measurements are as follows. Length of the head following the curvature of the surface one inch, of thorax nine lines and of pygidium nine lines. The proportional lengths of the head thorax and pygidium measured in this way would therefore be 4-1-1.
But if we measure the parts in a straight line from the middle of the anterior to the middle of the posterior margins, the length of the head is about nine lines, the thorax about eight and the tail a little more than seven.
The width of the head at the eyes in a straight line is one inch nearly ; following the curvature one inch and a half; width of axis of thorax about seven lines ; length of pleuræ about three lines and a half.
The only described species to which this bears any near resemblance is the well known I. crassicauda of Europe but on comparison I find that that species has a larger head, a narrower central lobe to the thorax, the axis of the tail distinctly defined all round