A HISTORY OF BEDFORDSHIRE 
Two reptiles have also been identified from the Chalk of the 
county, namely the common Cretaceous fish-lizard Ichthyosaurus campy- 
lodon, of which an imperfect jaw is known from the Totternhoe Stone at 
Chalton ; and the large short-necked pliosaurian Po/yptychodon interruptus, 
of which the large fluted conical teeth occur in the Chalk-marl. 
I am informed that Mr. W. Ransom of Hitchin has in his collec- 
tion remains of the cave-lion (Felis /eo spelea) and wild horse (Equus 
caballus fossilis) from Langford. 
Mr. J. S. Elliott has shown me a tooth of the above-mentioned 
saurian Ichthyosaurus campylodon and another of a shark from the Cam- 
bridge Greensand of Henlow ; and the coprolite-pits in that formation 
have doubtless yielded many other vertebrate remains similar to those 
from Cambridgeshire. 
Among the reptilian remains from the Potton Sands is included 
the base of a dinosaurian skull, described by Professor H. G. Seeley * as 
Craterosaurus pottonensis ; it is too imperfect to afford decisive evidence 
as to the affinity of the animal to which it belonged. Bones and teeth 
of the great three-toed bipedal reptile of the Wealden, the Iguanodon, 
occur not uncommonly in these deposits; as well as those of its 
carnivorous cousin Mega/osaurus. Crocodiles are represented by the 
huge Dacosaurus (or Geosaurus) maximus, of which the conical and 
carinated teeth have been washed out of the Kimeridge Clay and 
reburied in these deposits. 
Remains belonging to both groups of the great marine saurians 
characteristic of the Secondary period are also common in the Potton 
Sands. Of the ichthyosaurs, or group in which the head is large, 
the neck short, the eyes furnished with a ring of bones, and the bones 
of the paddles articulated together in a pavement-like manner, the 
Cambridge Museum possesses a fine series of remains from these 
deposits. Of the second group, or plesiosaurs, in which the neck is 
often long and the bones of the paddles are of more normal type, several 
forms are known. Among the long-necked and small-headed types are 
Colymbosaurus trochanterius, C. brachistospondylus and Murenosaurus trun- 
catus, all of which occur typically in the Kimeridge Clay. From the 
same formation are derived the large triangular teeth of P/osaurus—a 
short-necked and large-headed member of the group—which are of 
such common occurrence in the Potton beds. 
Scales, spines, palates and teeth of several kinds of Jurassic fishes 
are likewise met with in the Potton beds. Among these it will suffice 
to mention the large button-like teeth and polished rhomboidal scales 
of the Kimeridgian ganoid Lepidotus maximus, the palates of the pycno- 
dont ganoid Gyrodus cuviert, the elongated crushing teeth of the shark 
Hybodus obtusus, derived from the Kimeridge or Oxford Clay, and the 
dental plates of Ischyodus townsendi, a species belonging to the same 
group as the modern chimera, whose remains occur typically in the 
Portland Limestone of Wiltshire and Dorsetshire. 
1 Quart. Fourn. Geol. Soc. xxx. 183 (1874). 
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