36G Bibliographical Notices. 



Brachyura, and 3 of Anomura. On our coasts, at present, between 

 30 and 40 forms of the Crab, Lobster, and Shrimp tribes are known. 

 The MoUusca number 220 species, including 7 species of Nautilus, 

 of which latter only two living species are recorded. About 100 

 species of fossil fish are numbered, a large proportion belonging to 

 the Shark and Ray tribes, and others having affinities with those of 

 warmer latitudes ; while some forms resemble others now so plentiful 

 in the British seas, as the Herring, Eel, Cod, and Whiting. Between 

 eighty and ninety fossil fish have been obtained from the Isle of 

 Sheppey, — a limited area as contrasted with the whole British seas, 

 which contain about 160 species. Of Reptiles about fourteen spe- 

 cies now exist in England ; but twenty-one species occur in the London 

 Clay, of which eighteen belong to Turtles and Tortoises. There is 

 something suggestive in the fact, that while all the tropical seas of 

 the world have yielded but five species of marine Turtles, no less than 

 ten species have been found within a limited area in the London 

 Clay. 



Remains of birds and mammals are very scarce ; but the vegetable 

 kingdom furnishes us with a group as marvellous as those of fishes 

 and reptiles in the animal kingdom. Leguminous plants and Coni- 

 ferous trees were somewhat abundant, especially the former ; Palms 

 also, related to the Ni'pa ; while the Cotton- and Orange-trees had 

 their analogues ; and with them also occurred a proteaceous plant, 

 Petrophylloides, related to a group characteristic of the vegetation 

 of Australia. 



The third lecture continues in descending order the low'er London 

 Tertiaries, that variable and irregular group of marine, freshwater, 

 and estuarine origin, known as the Basement-bed, Woolwich and 

 Reading series, and Thanet Sands ; — the latter forming " imderneath 

 London and the adjacent districts a large and important water-bear- 

 ing stratum, — that which supplies all the early and many of the later 

 Artesian wells," the origin and principles of which are fully explained 



(P-^"8)- . , . , .... 



This portion concludes with certam theoretical considerations, in 



which the author dwells upon the probable extent of the old Chalk 

 area, — the seas, land, islands, and climatal conditions of the older 

 Tertiary and London-clay periods, and the subsequent changes in the 

 physical geography of the district around London. 



Originally given as lectures, and not intended at first for publica- 

 tion, Mr. Prestwich naturally avoided any details that would be un- 

 interesting to his audience (which can be readily appended in any 

 future edition) ; his intention, which is successfully carried out, being 

 to interest his hearers in the general geological principles, and 



author of this valuable monograph should not have fully availed himself of 

 some of the fine specimens of fossil Crustacea from the London Clay in 

 the Hunteiian Collection of the Royal College of Surgeons, as additional 

 objects of illustration for his memoir, — specimens collected at so early a 

 period, and evincing the interest which the great comparative anatomist 

 took in this portion, as he did in every other, relating to the fossil relics of 

 past creations. 



