58 



ERA OF THE OOLITE 



strata of themselves. The crinoidea and echiniteg were 

 also extremely numerous. Shell mollusks, in hundreds 

 of new species, occupied the bottoms of the seas of those 

 ages, while of the swimming shell-fish, ammonites, and 

 belemnites, there were also many scores of varieties. The 

 belemnite here calls for some particular notice. It com- 

 mences in the oolite, and terminates in the next forma- 

 tion. It is an elongated, conical shell, terminating in a 

 point, and having, at the larger end, a cavity for the resi- 

 dence of the animal, with a series of air-chambers below. 

 The animal, placed in the upper cavity, could raise or 

 depress itself in the water at pleasure by a pneumatic 

 operation upon the entral air tube pervading its shell. 

 Its tentacula, sent abroad over the summit of the shell, 

 searched the sea for prey. The creature had an ink-bag, 

 with which it could muddle the water around it, to pro- 

 cect itself from more powerful animals, and strange to 

 say, this has been found so well preserved that an artist 

 has used it in one instance as a paint, wherewith to de- 

 lineate the belemnite itself. 



The Crustacea discovered in this formation are less nu- 

 merous. There are many fishes, some of which (acrodus, 

 psammodus, &c.,) are presumed from remains of their 

 palatal bones, to have been of the gigantic cartilaginous 

 class, now represented by such as the cestraceon. It has 

 been considered by Professor Owen as worthy of notice, 

 that, the cestraceon being an inhabitant of the Austrilian 

 seas, we have, in both the botany and ichthyology of this 

 period, an analogy to that continent. The pycnodontes 

 (thick-toothed) and lepidoides, (having thick scales,) are 

 other families described by M. Agassiz as extensively 

 prevalent. In the shallow waters of the oolitic formation, 

 the ichthyosaurus, plesiosaurus, and other huge saurian 

 carnivora of the preceding age, plied, in increased num- 

 bers, their destructive vocation.* To them were added 

 new genera, the cetiosaurus, mososaurus, and some others, 

 all of similar character and habits. 



Land reptiles abounded, including species of the ptero- 

 dactyle of the preceding age — tortoises, trionyces croco- 



* In some instances, these fossils arefound with the contents of 

 the stomach faithfully preserved, and even with pieces of the ex 

 ternal skin. The pellets ejected by them (coprolites) are found in 

 vast numbers, each generally enclosed in a nodule ironstone, and 

 sometimes showing remains of the fishes which had formed their 

 food. 



