﻿16 T. Davidson — On New Scottish BracMopoda. 



The muscular impressions in Oholus are more spread out than in 

 either D«sc/na or SipJionotreta, and Prof. King thinks that this difference 

 appears to be explained, thus : the latero-cardinal scars in SipJionotreta 

 are more crowded together than they are in Oholus, and the central 

 jDrojecting portion of the undercut ' spectacle '-like impressions in 

 Oholus advance more to the anterior margin of the valve than the 

 corresponding imjDressions in SipJionotreta. 



2. LiNGTJLA Canadensis, Billings (?). PL II. Figs. 4, 4a. h. 

 Lingula Canadensis, Billings, Geological Survey of Canada, Fossils, 

 vol. i. p. 114, fig. 95, June, 1862. 



Of this large and beautiful Lingula Mrs. Gray has found one in- 

 complete example. It was obtained from the Breccia-conglomerate 

 of Balcletchie, near Girvan, in Ayrshire. This conglomerate rests 

 upon the rock at Balcletchie, which, some geologists have considered 

 to be of Llandeilo age. 



It is not possible to describe the complete shape of the fossil, 

 because the two anterior thirds of its valves are alone preserved. It 

 however, so nearly agrees in size, shape, and sculpture with the 

 fossil described and figured by Billings from the Hudson Eiver 

 group of Anticosti, that we have thought it preferable to leave it 

 provisionally under that designation. 



It is of a quadrate or sub-pentagonal elongated shape, posteriorly 

 obtusely acuminated, broadest anteriorly; the sides are almost 

 straight, front very slightly convex with broadly rounded angles. 

 The smaller valve is much flattened anteriorly, and but slightly 

 convex posteriorly or towards the beak. The larger valve is very 

 much more convex. The surface of both valves is covered with fine 

 bead-like longitudinal radiating ridges, with shorter and narrower 

 ones occasionally intervening between each larger pair, and esjDecially 

 so in the proximity of tlie front and lateral margins. From five to 

 eight of these ridges occupy the breadth of a line. The interspaces 

 between the longitudinal ridges are about three times the width of 

 each ridge, and from each of the bead-like projections, are horizontal 

 or concentric much narrower rounded ridges with interspaces of 

 about equal breadth; as seen in the enlarged drawing. Fig. 4&. of 

 our Plate. 



The two perpendicular and horizontal ridges producing on the 

 surface of the valves a beautifully reticulated sculpture, to which 

 the rows of bead-like projections give additional prominence. 



In size, Mrs. Gray's specimen, when complete, cannot have 

 measured much less than one inch and nine lines in length, b}'- one 

 inch and three lines in breadth. These proportions recall those of 

 X. tenuigranulata, M^Coy, a closely allied species, and which would 

 differ from the one under description by its much more finely and 

 closely reticulated sculpture. 



3. Lingula quadrata, Eichwald. PI. II. Figs. 2, 3. 

 Crania quadrata, Eichwald, Zool. Specialis, vol. i. p. 273, pi. 4, fig. 2. 



1829. 

 Lingula quadrata, De Verneuil, Geol. of Eussia, vol. 2, pi. i. fig. 10. 

 1845. 



