THE SILURIAN ROCKS OF SOUTHWEST SCOTLAND. 449 



Wenlock rocks of the southeast border of Scotland their remains are 

 often found associated with such graptolites as Monograptus priodon, J/. 

 Flemingii, and Retiolitet Geinitzianus, and witli Orthoceratites, in thinly- 

 laminated dark shales which weather into layers as fine as writing paper. 

 In their Monograph on the British Fossil Phyllocarida Professor Jones and 

 Dr. Woodward make a new genus, Calyptocaris, 1 to include the form recorded 

 by R. Etheridge, Jnr., as Dithyrocaris (?) striata? which was obtained by the 

 Geological Survey from Carmichael Burn near Carmichael Manse, to the 

 north of Tinto in Lanarkshire. In 1873, at the time of the publication of 

 the " Explanation " of Sheet 23, these beds were considered by the Geological 

 Survey to belong to the Lower Old Red Sandstone formation, 3 but their 

 subsequent work has shown them to be the uppermost zones of the Ludlow 

 shales, which, together with the Downtonian rocks, make their appearance 

 upon the back of a denuded isoclinal fold in the midst of Lower Old Red 

 strata. 4 



OSTRACODA. 



In the Girvan area ostracoda have been found on several horizons. The 

 lowest horizon is that of the Stinchar limestone which at Aldons lime- 

 works near Pinmore has yielded five species of the genus Cy there and one 

 species of Primitia which Professor Rupert Jones considers to be of 

 eminently Lower Silurian type. 



From the Middle Caradoc shales of Whitehouse Bay Mrs. Gray has obtained 

 the following forms Aparchites leperditioides, A. subovatus, Beyrichia impar, 

 Cypridina Grayae, Primitia elongata, var. nuda, P. girvanensis, P. Grayae, 

 P. Krausei, P. mundula, var. fimbriata, P. mundula, var. Kloedeniana, P. 

 ulrichiana, and Sulcuna praeurrens. 



In the uppermost Caradoc rocks of Threave is the first appearance of the 

 genus Beyrichia^ represented by B. comma, and the common Upper Silurian 

 form B. Kloedeni. 



In the Upper Silurian rocks of Girvan and Straiten, in the Bargany Pond 

 Burn, in shales at the top of the Llandovery Rocks, a variety of Beyrichia 

 Kloedeni occurs, and the Wenlock rocks of Straiten have yielded the familiar 

 forms Beyrichia Kloeden ?', B. (Entomis) impendens, and Entomis globulosa. In the 

 main it would appear that these early entomostraca seem to have frequented 

 the same kind of sea-bottom as that sought out by the trilobites, as their 

 remains are obtained from the same localities and the same beds. 



In areas outside that of Girvan entomostraca swarm in some of the 

 Wenlock-Ludlow beds of the Lesmahagow and Hagshaw inliers of Lanark- 

 shire, but they are restricted to one or two species, Beyrichia Kloedeni and 

 one of its varieties being the principal forms. A species of Entomis also 

 occurs. A species of Beyrichia is rare in the Downtonian fish-beds. 



CIRRIPEDIA. 



Two species of Turrilepas have been found in the Lower Silurian rocks of 

 Girvan at Balclatchie, Whitehouse, and Drummuck, and an unnamed species- 

 from the Newlands beds in the Llandovery rocks. 



1 Palaeontolographical Soc., vol. liii., p. 183, pi. xviii., fig. 7, 1899. 



2 Memoirs Geol. &urr. Scot. " Explanation " to Sheet 23, pp. 57 and 100. 



3 Ibid., p. 14, par. 24. 



4 Mem. Geol. Surv. U.K., vol. i., pp. 586-588. 



2F 



