46 NATURAL SCIENCE [j ULY 



be the proper one for the doubtful group ; we may not, for that 

 reason alone, boldly assert that they are Marsipobranchs. Nor 

 again will it be held to be sufficient in the opinion of most zoo- 

 logists to say " Mr X. was a very gifted man, and he used to say 

 that the so-and-so's are really such-and-such." It really is time 

 for Mr Smith Woodward to give us more solid reasons than such 

 as these for classing Ostracodermi with Marsipobranchii. 



I shall be surprised if he can do so ; for I have turned the 

 matter over carefully and happen to have a rather intimate 

 acquaintance with both the Ostracodermi and the Marsipobranchii. 

 I am unable to find a single fact which can be considered as 

 positive evidence of affinity between the two groups. 



It is true that we do not know of the existence of paired fins 

 in the Ostracodermi — -nor in Marsipobranchii — but though the 

 supposed pectorals of Cephalaspis are probably not to be regarded 

 as pectorals, we are not in a position to assert that Pteraspis had 

 no lateral fins, nor that the ' flippers ' of Ptcrichthys do not 

 represent such organs. 



Before the proposition favoured by Mr Smith Woodward could 

 be seriously discussed in the terms in which it is stated, it 

 would be necessary to show that the Ostracodermi are a natural 

 group, and no one can pretend that this is the case. The Cepha- 

 laspids, the Pteraspids, and the Pterichthyicls were originally asso- 

 ciated as ' Ostracodermi ' for purposes of mere temporary con- 

 venience. It is a question whether in these days of an avowed 

 genealogical implication in our classifications, such ' lumber- 

 rooms ' as ' Ostracodermi ' are permissible. I think not. There 

 is absolutely no reason for regarding Cephalaspis as allied to 

 Pteraspis beyond that the two genera occur in the same rocks, 

 and still less for concluding that either has any connection with 

 Pterlchthys. 



If, in view of this fact, we consider in a more detailed way the 

 suggestion of Cope, acclaimed by Smith Woodward, we find that it 

 amounts to the assertion, that there are evidences of the close genetic 

 relationship of the Marsipobranchii with either the Cephalaspids, or 

 the Pteraspids, or the Pterichthyids — or possibly with all of them. 



So far as I am aware the only satisfactory evidence of marsi- 

 pobranch affinities which one could expect to be offered by fossil 

 remains of palaeozoic date, is the presence of a single median nasal 

 aperture. The characteristic monorrhine structure of the marsi- 

 pobranchs might have been recorded in the preserved remains of an 

 armoured marsipobranch, had such a creature ever existed. Is there 

 any evidence of such a single nostril in Pteraspids, or Cephalaspids, or 

 Pterichthyids ? Most assuredly there is not. There is no aperture in 

 the cephalic shields of any of these forms which can be assigned to 



