Reviews — Bono's Dinosauna of Bernissart. 83 



•astragalus, and os calcis, the relation of the fibula to the tibia and 

 other osseous characters, could only be regarded as generic 

 •characteristics. More mature consideration has only deepened my 

 conviction that the Iguanodon Prestwichi is not an Iguanodon in the 

 sense in which the term Iguanodon should be used as a generic 

 distinction. There would be an end of zoological method if organic 

 differences of the magnitude which divide this animal from the 

 Iguanodon Mantelli could be classed as specific characters. The 

 earlier writers made species in this way ; but it was by the institu- 

 tion of a method altogether distinct from that used in the modern study 

 of existing life. I believe it to be imperative that no such difference 

 of method should prevail in the study of existing and extinct 

 animals, and therefore contend that, since the structures which I 

 have named differentiate the Kiinmeridge Clay animal so that 

 it would have been referred to a new genus had it been an existing 

 animal, we have no choice but to class it as a genus, though no name 

 has as yet been proposed to designate its characteristics. Similarly, 

 when the Memoir on Iguanodon Seeiyi was read before the 

 Geological Society, two years later, I suggested that it would have 

 been safe to have constituted it also as a new Dinosaurian genus. 

 I therefore find myself differing from M. Dollo, not so much upon 

 the results of his own work, as upon matters in which he depends 

 upon and has the support of one of our most accomplished and most 

 cautious comparative anatomists. But when the value of the character- 

 istics of these two Iguanodon types, which M. Dollo has so well 

 contrasted, is estimated, I am tempted to ask, is there any living 

 reptilian genus which in the skeletons of its species comprises so 

 wide and varied an assemblage of diffei'ential characters ? If the 

 differences were limited to one series of characteristics, or to one 

 region of the body, we might accept them as specific ; but when 

 they range through all parts of the skeleton, so as to imply many 

 differences in the soft parts of the body, I cannot but reiterate that 

 the close correspondence between Iguanodon Bernissartensis and 

 J. Seeiyi sustains my earlier belief that the larger Belgian type 

 constitutes a new genus. The form of the head, of the nares, of the 

 orbit, of the temporal vacuities, of the pre-dentary bone, in Iguanodon 

 Mantelli, all seem to me generic characters ; and the elevation of the 

 nasal bones into a sharp crest may be of similar importance, seeing 

 its relation to the nasal crest or horn in Ceratosaurus. These 

 characters are sustained by the proportions of the several parts of 

 the ilium, the form of the prepubic bone, the shape of the femur and 

 position of its third trochanter, no less than by the characters of the 

 scapular arch and the metacarpal bones. The taxonomic value of 

 these characters should be beyond question. 



If I am right in my exposition that two of the three species 

 which have hitherto been referred to Iguanodon belong to new 

 genera, then it necessarily follows that I am unable to accept either 

 the data with which M. Dollo works, or the conclusions at which he 

 arrives in consequence, in so far as this concerns the classification. 

 It is unnecessary to define my view by suggesting names for these 



