94 



satisfactorily that it exists considerably lower than even Quenstedt had 

 ventured positively to place it. 



There can be no doubt, that the great confusion of ideas which has 

 existed with regard to what we consider to be one species, as evidenced 

 by the hosts of synonymes for it, to which we have been compelled to 

 refer, arose from that love of species making which characterized most 

 of our earlier Palaeontologists. No sooner did an abnormal form present 

 itself, than it was seized upon and named as a new species, whilst the 

 examination of the series would have shown its true connection with 

 common types. In species of which the number varies so much indi- 

 vidually, as in the oyster tribe generally, this precaution is most 

 essential, to enable us to arrive at safe conclusions in this respect : the 

 most symmetrical forms having been set up as types, whilst, in point of 

 fact, these are rather exceptional than otherwise. 



We can convince ourselves in the instance of G. incurva that this 

 shell is capable of assuming every shape between that of a flat oyster 

 and one of so different a development, as to have suggested the propriety 

 of conferring upon the individuals exhibiting it, a distinct generic name. 

 It has been shown, how the entire character of the shell has been affected, 

 by circumstances which enforced upon it a more or less permanent 

 adhesion to the body to which it had primarily attached itself; — that 

 the lateral iurrow, upon the presence or absence of which specific 

 differences have been supposed to depend, is one of the most fallacious 

 characters upon which they can be based. We can perceive that the 

 differences between the assumed species of G. incurva, obliquata, Maccul- 

 lochii, and cyrabium, are less than those existing between the young, 

 half-groAvn, or adidt states of either. We know that other creatures, 

 inhabiting the same sea zones, pass upwards from the point at which 

 they first appear, through a greater, or at least as great, a stratigraphical 

 range as either of these. Do Ave not then rightly pause before we draw 

 sharp lines of demarcation, whilst neither the facts presented to us in 

 the formation Tinder consideration, nor our knowledge of physiological 

 facts, as exemplified in the existing Hfe of our own epoch, afford us any 

 valid pretext for so doing ? 



To show in the clearest possible manner the nature of the differences 

 to which we have just alluded, we here refer to a diagram constructed 

 expressly for the purpose, representing Gryphsea incurva of the best 

 known type, and fiillest dimensions. By uncovering the drawing from 

 its upper portion downwards, may be made to appear in succession, first, 

 its oyster condition ; secondly, that of Gryphsea suilla ; thirdly, that of 

 G. obliqua, young ; fourthly, that of G. obliqua, adult ; fifthly, G. incurva, 

 half-grown; sixthly, ditto two-thirds grown; seventhly, adult ; eighthly, 



