PALAEONTOLOGY 



county likewise includes many extinct generic types of the class, 

 such as Cerotnya, Cypricardia, Gresslya, Homomya, and JJnicardium. The 

 brachiopods comprise Rhynchonella concinna, and several species of Tere- 

 bratula, among the latter being T'. digona and obovata. The sea-urchins 

 are represented, among other types, by the small Echitiobrissus cluni- 

 cularis, the large Clypeus muelleri and plottii, and three species of the 

 large-spined genus Acrosalenia. Among plant remains, mention may 

 be made of the fruits described as Carpolithes and Caidacarpum ooliticum. 

 Taken altogether the fauna of the Great Oolite presents a distinctly 

 sub-tropical aspect, the moUuscan genus Trigonia now surviving only in 

 Australian waters, while Pleurotomarla is known only by a few speci- 

 mens dredged now and again from the warmer seas. 



The lists of fossils given by Mr. Sharp from the Lincolnshire 

 Limestone, Collyweston Slate, and Northampton Sand (mainly repre- 

 senting the Inferior Oolite, although the upper portion of the latter, 

 together with the overlying Upper Estuarine Group, is usually classed 

 with the Great Oolite) are even larger than those of the Great Oolite. 

 Mr. R. Etheridge, who, in his Presidential Address to the Geological 

 Society in 1882,' gives eleven localities in the county where the fossils 

 of the Lincolnshire Limestone are most common, states that ' only four 

 species of ammonites are known, A. murchisonce, A. subradiatus, A. blag- 

 deni, and an undescribed form from Duston. Nautilus is represented by 

 two species only, N. obesus and N. polygonalis ; the Crustacea by two 

 species ; the Asteroidea [star-fishes] only by Astropecten cottsiuoldia stam- 

 fordensis. On the other hand, the Mollusca proper, in all three groups, 

 show a large fauna ; the species of Gastropoda obtained from the Barnak 

 Rag number 66 and illustrate 17 genera; from the well-known cut- 

 ting at Ponton 20 genera and 64 species are recorded. The Gastropoda 

 through the 11 localities number 75 genera and 218 species; the 

 Lamellibranchiata Monomyaria [single-muscled bivalves] 63 genera and 

 133 species; the Dimyaria [double-muscled bivalves] 112 genera and 

 211 species. The Brachiopoda have little specific value; in no in- 

 stance have more than eight species occurred in one locality. 

 The slates of Collyweston succeed the Lower Estuarine Group 

 [Northampton Sand] ; the twelve or fourteen recognized beds hold 

 well-defined species, among them being Natica cincta, Unicardium 

 impressum, Cardium buckmani, the highly characteristic Pteroceras bentleyi, 

 Trigonia compta, Homomya unioniformis, and Astropecten cottsivoldia stam- 

 fordensis. Pecopteris polypodioides [a fern], with its fronds in fructifica- 

 tion, is abundant in the uppermost beds.' With such a multitude of 

 forms to deal with, it would be little use quoting the names of other 

 species from these formations, but it may be added that while the 

 Northampton Sand includes Ammonites murchisonce of the Lincolnshire 

 Limestone, it likewise contains the Upper Liassic A. bifrons. 



The fossils of the Northamptonshire Lias are of a less distinctly 



^Proc. Geol. Soc, 1882, p. 65. 

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