CARBONIFEROUS DISTRICT OF COLCHESTER AND HANTS. 259 



from the habits of its living repi'esentatives, intended to inhabit 

 the depths of ocean. The presence of fossil shells of this tribe 

 is therefore considered by all geologists as conclusive evidence that 

 the deposits in which they occur were formed in the bottom of the 

 open sea. Above this limestone, in the order of succession, we have 

 alternations of marls and limestones, and next a bed of white crystal- 

 line gypsum, contrasting strongly in its purity and whiteness with the 

 other beds of more mechanical origin. Here the shore becomes low 

 and no rock is seen, but a little to the eastward we find the great 

 gypsum quarries of Windsor, excavated in the outcrop of a very thick 

 bed, the strike of which would bring it out to the shore just where 

 our section fails, and where the gypsum has been removed partly by 

 the river and partly by the quarrymen who earliest dug this rock for 

 exportation. A little farther to the southward, at the next bluff point, 

 there is a very thick bed of limestone, filled with, or rather made up 

 of, fossil shells of various species and genera, affording a remarkably 

 perfect display of the shelly coverings of the creatures that inhabited 

 the Carboniferous seas. 



A descriptive list of the species found here and elsewhere in Nova 

 Scotia, in limestones of this age, will be appended to this chapter, 

 with figures of several of the more characteristic species ; and in this 

 place I shall merely mention them generally, and with reference to their 

 living analogues. 



At the head of these ancient Molluscs is a Nautilus, to a cursory 

 observer not unlike the ordinary Nautili of the Indian Ocean ; nor are 

 these ancient Nautili inferior in dimensions to their modern I'elatives, 

 for at "Windsor they may sometimes be seen as much as six inches 

 in diameter. With the Nautilus, we may occasionally find species 

 of Ot'thoceras, a shell of the same family, but straight instead of 

 being whorled. The species usually seen is about one -fourth of an 

 inch in diameter, and four or five inches in length ; but I have seen 

 specimens nearly an inch in diameter. The Orthoceras as well as the 

 Nautilus was a chambered or partitioned shell, intended to serve as a 

 float as well as a protection to the animal, which could thus sport on 

 the surface of the sea as well as creep upon its bottom. The inner 

 chambers of these shells ax'e now empty or incrusted with crystals of 

 calc-spar ; but the outer chambers are filled with hard limestone, often 

 containing numbers of smaller shells. A species of Conularia is 

 also found in this limestone, though less abundant here than in 

 some other places to be hereafter noticed. This shell is believed to 

 have belonged to an animal of the class Pteropoda, which contains 

 little swimming molluscs, furnished with a pair of fins or flappers for 



