156 



prise forms (Leptolepis saltviciensis) related to the Herring, 

 and others related to the Sturgeon and the Bow-Fin of the 

 United States. 



But it is for the Reptiles that the Upper Lias is so celebrated, 

 and the species which then flourished are now extinct. The 

 most important of them are undoubtedly the Fish Lizards, 

 or Ichthyosauri, of which six species have been obtained 

 from the Upper Lias of Cleveland. The Ichthyosaurus was 

 a huge carnivorous animal, often attaining a length of twenty 

 feet, and it is worthy of note that these great marine reptiles 

 were of a very fish-like shape and even provided with fins, 

 as some specimens from the Lias of Wurtemberg have shown. 



Less numerous in species than the Fish Lizards and 

 probably less ferocious, were the Plesiosaurs, differing from the 

 former in having long flexible necks. Besides these there were 

 several reptiles closely related to the modern Crocodiles, as 

 well as Flying Dragons {Scapkognathus) , the remains of which 

 have all been discovered in the Alum Shale. 



There is a curious feature connected with the fauna of this 

 stratum, tending to show that even in a limited area like 

 Cleveland, different conditions of life must have prevailed 

 even during the deposition of one bed. At Peak and Whitby, 

 and alone; the coast generally, the common fossils of the Alum 

 Shale are extremely numerous, but on Carlton Bank they are 

 very scarce, even Leda ovum, the typical bivalve of the horizon, 

 being very far from abundant. Evidently the life conditions 

 must have been less favourable in the western, than in the 

 eastern part of our area during Upper Liassic times. 



The fauna of the Inferior Oolite (see Table 4) is less rich 

 than that of the Lias, owing to the Estuarine conditions 

 under which it lived. The records are to be found in thin 

 marine strata intercalated between massive grits and sand- 

 stones, the chief of them being the Dogger, the Filer Beck 

 Bed, the Millepore Bed, and the Grey Limestone Series. 

 Different suites of animals occur in each of these, and the 

 most striking featui'e of the Bajocian fauna as a \* hole, is its 

 richness in bivalves, in this respect even exceeding the Lias. 



