84 



MIDDLE LIAS. 



Brachiopoda. 



Terebratula punctata, Sow. 



Rhynchonella tetrahedra, Sow. 



— variabilis, Schloth. 



— acuta. Sow. 

 Lingula Beanii, Phil. 



resupinata, Sow. 

 cornuta. Sow. 

 Edwardsii, David. 



ECHINODERMATA. 



Heraipedina Jardinii, Wr. 



Pentacrinus subangularis. Mill. 



The Marlstone attains a great development in Yorkshire, and is fully exposed in 

 the coast section near Staithes. " The sandy, conchiferous marlstone beds," says Prof. 

 Phillips,^ " which in Colborn Nab cover the Lower Lias shale, are seen rising with it and con- 

 tributing to swell the altitude of Boulby and Rockcliff". The lower part of this series is 

 generally the most solid, and projects in broad, compact floors above the Lias. On the 

 surfaces of such beds lie innumerable multitudes of Oysters, Dentalia, Pectens, Cardium 

 tnmcatum, Avicula itmquivalvis, and, more rarely about Staithes, beautiful fossil star-fishes 

 af the genus OpMura." In Boulby CHfFs^ the ironstone and Marlstone series consists of — 



a. The ironstone bands, which are numerous layers of firmly connected nodules of 

 ironstone, often septiarate, and enclosing dicotyledonous wood, Pectines, Aviculse, 

 Terebratulge, and from twenty to forty feet thick. 



b. The Marlstone series, consisting of alternations of sandy Lias shale and sandstones, 

 which are frequently calcareous, and generally full of shells. The lower beds are usually 

 most solid, and project from the cliffs in broad floors, covered with Pectens, Cardia, Dentalia, 

 Aviculse, Gryphsese, &c. The thickness variable from forty to 120 feet. 



The molluscan fauna of these beds closely resembles the list already given from the 

 Marlstone of Gloucestershire. Among the Echinodermata, however, are found species which 

 appear to be limited to the Yorkshire series, as Uraster carinatus, Wr., Astropecten 

 Hastwgsia, Porb., Opldoderma Milleri, Phil., Aspidura loricata, Will., and OpJdura 

 Murravii, Forb., all collected from the Marlstone series near Staithes. 



The zone of Ammonites margariiatus is exposed at Toad's Cove, Down Cliffs, near Brid- 

 port Harbour, Dorset ; its position is shown in the section, p. 77, where the rock-bed 

 contains Ammonites margaritatus and many of the same species of Conchifera found 

 associated with that Ammonite, in other Marlstone districts. The star-fish-bed, with 

 Opldoderma Egertoni, Brod., and Ammonites fimhriatus, Sow., is seen beneath the rock- 

 bed of the Marlstone series. 



1 'Geology of Yoilcsliire,' p. 101. 



2 Ibid., p. 102. 



