442 Dr. G. C. Wallich on the supposed Vertebrate Lower Jaw. 



In order to show how diverse were the opinions expressed, 

 I may mention that the specimen was pronounced to he — the 

 mandible of a fish, a portion of the lingual ribbon of Mitra, a 

 claw of a minute Crustacean, part of the manducatory appa- 

 ratus of Notommata or an allied species, and, lastly, a valve of 

 a redicellaria ; some of the advocates of these conflicting judg- 

 ments still retaining their views unchanged. 



To Mr. Busk is due the merit of pointing out the extremely 

 close analogy between the object in question and certain Pedi- 

 cellariae, — his intimate acquaintance with every kind of minute 

 organic structure leading him to regard its Pedicellarian origin 

 at all events as highly probable, if not certain. 



On being made aware of Mr. Busk's opinion, I immediately 

 examined the Pedicellarise of Echinus lividus, of which I possess 

 a specimen obtained in the same locality. The valves, although 

 not identical, bear a sufficient resemblance, both in configuration 

 and detail, to satisfy me of the probable accuracy of Mr. Busk's 

 view ; at the same time I think it better to reserve my final 

 determination of the structure, pending still further inquiry and 

 comparison. 



The communication on the subject by Mr. C. Spence Bate 

 (politely submitted to me, at his request, prior to its publication 

 in the present Number of the ' Annals') will show how far the 

 occurrence of pseudomorphs in the organic world should put us 

 on our guard against hasty generalisation founded on semblances 

 in figure alone. 



In the case more immediately under notice, I was by no 

 means insensible to the facts that the appearance of minute 

 teeth along the greater portion of each ramus of the supposed jaw 

 might be due, in reality, to simple serrature of its margin, and 

 that the true texture of vertebrate bone was not visible in its 

 substance. But, on the other hand, it seemed unreasonable to 

 assume that absolute identity in structural detail should exist 

 between an object of such minute dimensions and the homolo- 

 gous parts of the larger animals to which it is allied. Or, even 

 assuming that the intimate structure must be identical in type, 

 we might fairly suppose that minute details, observable only 

 under the microscope in the larger orders, would become so in- 

 ordinately reduced in size in an organism already microscopic, 

 as to be invisible. 



The figure accompanying my former note, although accurate 

 as a sketch, fails to convey the full extent of the resemblance to 

 a jaw, the projecting digitate-like processes in the region corre- 

 sponding to the articulation being too jagged, and the serrature 

 too saw-like. 



Probably the true figure of the object, seen from above, is that 



