128 Technicalities of Fossil Shells, 



in Fig. 12, the diameter of the masses being from one to twelve or more 

 inches. It is found abundantly in the Black River Limestone, generally 

 accompanied by Columnar ia alveolata, but as its internal structure has not 

 yet been explained, the family X)f coral to which it may belong cannot be 

 pointed out. The generic name is from stroma, a layer or lamina ; and 

 cerion, a honey-comb. 



The above five species of fossil corals are those most commonly met 

 with in the Lower Silurian rocks of Canada. There are a few other species 

 DOt so abundant, which will be described hereafter. 



On turnino- back tt the dassification of the animal kingdom criven on 

 page 31, it will be seen that the department Radiata is divided into three 

 classes Sea-urchins, Jelly-fishes, and Polyps. The latter are also subdivided 

 into three orders, Hijdroids, Actinoids, and Rhizopods. The Trenton Lime- 

 stone corals are all Actinoids, with the exception of the last one described. 

 Stromatocerium rugosum, the true position of which has not yet been ascer- 

 tained. From the descriptions above given, it is not difficult to understand 

 why the corals should be called radiated animals. 



ARTICIiE XYIQ. — On some of the technical terms used in the description 



of Fossil Shells. 



The language used in the science of palaeontology appears to the begin- 

 ner unintelligible, and devoid of interest, but when understood, it will be 

 found full of meaning and exceedingly convenient. In the description of 

 fossil shells, although at fii-st sight one is liable to be impressed with the idea 

 that there are a great many hard words to be learned yet upon a further 

 acquaintance with the subject, this difficulty will appear to have been over- 

 rated. There are in fact in this extensive branch of Natural History only a 

 few technical terms in use, and most of these may be comprehended after a 

 few minutes study. 



It is not necessary in this work to enter into a detailed iuterpretatiou 

 of such words as hemispheric, cylindrical, tumid, gibbous, quadrate, sub- 

 quadrate, rhomboidal, sub-romboidal, globose, or sub-globose. Nearly all 

 general readers are eitiier already acquainted with the meaning of these, or 

 by reflecting a moment may arrive at their import, or by referring to any 

 good dictionary of the English language, ascertain the sense in which they 

 are used. It maybe proper to state that the prefix " sub," is used to denote an 

 inferior degree, as in the words quadrate, approaching in form to the square 

 and sub-quadrate, not so near the square as quadrate. The possession of a 

 good dictionary and the habit of referring to it will be found sufficient for 

 the greater number of cases. Unless, however, the reader is also a collector, 

 the explanations will be of no practical value. Specimens may be coUectetl 

 from almost every quarry or exposure of rock in the settled portions of this* 

 country. We would strongly recommend some attention to this pursuit 

 during those leisure hours of which most persons have more or less; 



