1397] TAXONOMIC POSITION OF PTERASPIDAE, ETC. 47 
the nostril. If these fishes possessed a nostril, single or double (as 
presumably they did), it seems that it was placed in such a position 
as to avoid perforating the bony shields of the head. To assume—in 
the total absence of evidence pvo or con—that these fishes were 
monorrhine, is surely illegitimate and arbitrary. Further, there 
are in Hukeraspis and some other head-shields indications of lateral 
chambers, remotely suggesting lateral branchial chambers; but the 
form and position of these would be equally consistent with 
elasmobranch as with marsipobranch affinities. 
It seems to me that even Huxley’s cautious statement as to the 
affinities of Pteraspis and Cephalaspis goes too far. He says 
(Quart. Journ. Geol. Soc., vol. xiv., p. 279), “ A careful consideration 
of the facts, then, seems to me to prove only the necessity of sus- 
pending one’s judgment.” So far I entirely agree with him. He 
proceeds, “ That Cephalaspis and Pteraspis are either ganoids or 
teleosteans appears certain, but to which of these orders they 
belong there is no evidence to show.” That was written a long 
time ago. It seems to me that whilst there is abundant evidence 
to shew that Pteraspids and Cephalaspids, and also Pterichthyids were 
eraniate vertebrates, there is nothing to show conclusively that they 
are referable to any known group of fishes, rather than that they 
are to be regarded as representatives of isolated extinct lines of 
descent. Their possession of paired orbits, fish-like scales, and fish- 
like median fins, renders it the course involving least assumption con- 
cerning matters of which we are ignorant, to treat them as detached 
groups of primitive fish-like forms, concerning the closer relation- 
ships of which judgment must be suspended. 
The palaeontologist is, we must admit, entitled to make sug- 
gestions and guesses as to the affinities of the organisms which have 
left behind them the fragments with which he has to deal. On 
the other hand, if he aspires to be a zoological taxonomist he must 
accept the common point of view of zoologists. He does injury 
rather than benefit to zoological science when (as is, unfortunately, 
sometimes the case) he endeavours to impose an unwarranted 
“guess” upon zoological taxonomy as though it were a soberly 
worked-out conclusion, or reconstructs classifications hitherto based 
upon the consideration of comprehensive anatomical data, in order 
to give unnatural prominence to. such characteristics alone as are 
furnished by the hard parts of organisms—parts with which a 
study of fossil forms renders him specially familiar. 
E. Ray LANKESTER. 
