of the Ichthyosaurian Head. 267 



be supposed to be confluent. But even with this view there 

 remains an improbability against the nostrils being mesially 

 divided by the principal frontal bones, inasmuch as it is only 

 among mamiuals, from which the prefrontal and postfrontal 

 bones have disappeared as separate elements, that the frontal 

 bone ever enters into the anteorbital vacuity. Prof. Cope, by 

 what is probably an oversight in lettering the figure, makes 

 the lachrymal bone enter the alveolar border and carry teeth, 

 by which it is excluded from entering into the orbit. These 

 relations are so entirely unparalleled, that I can only account 

 for the determination on the supposition that, in printing, the 

 letters intended for the maxillary and lachrymal bones became 

 interchanged. On this view, the anterior narine would be 

 sun-ounded by the premaxillary, frontal, nasal, and lachrymal 

 bones — though, according to the lettering, for lachrymal we 

 should read maxillary. 



Now, do the Em-opean Ichthyosaurs support the interpre- 

 tation which Prof. Cope makes from a head from the Lias of 

 Barrow-upon-Soar ? I do not find such a bone in any of the 

 materials (drawings, photographs, and specimens) to which I 

 have access ; and these include species from several formations, 

 both English and French. I do not wish to urge this nega- 

 tive evidence as proof that the bone does not exist, but only 

 to show that, if it does exist in Prof. Cope's specimen, he 

 possesses an animal which differs in remarkable generic cha- 

 racters from Ichthyosaurus. And this view might be regarded 

 as supported by the figure ; for we miss from its place, poste- 

 rior to the postorbital bone, an osseous supraquadrate element 

 which has hitherto been found to mark every Ichthyosaurian 

 cranium. And Prof. Cope's other modifications all point in 

 the same direction, and make an animal which mimics Ich- 

 thyosaurusj but differs from that type in all its most essential 

 characters. Thus, in the new Barrow specimen, the squa- 

 mosal bone takes upon itself the ordinary functions of the 

 parietal, whereas in Ichthyosaurus the squamosal is much 

 such a bone as it is in the Teleosauria ; and in no Ichthyosaur 

 known to me do the squamosal bones extend up the side of 

 the cranium and meet mesially, as they are shown to do in 

 one of Prof. Cope's figures. In consequence of this identifi- 

 cation, all the superior cranial bones are moved a place back- 

 ward, what were regarded as parietals now being squamosals; 

 the frontals are parietals, and the nasals frontals, while the 

 nasals are replaced by the new bones already discussed. 



In view of the supposition that we have here a new 

 genus, it is difficult to believe that a naturalist so acute and 

 accomplished as my friend should have overlooked such a 



19* 



