296 ]\Jr. G. A. Boulenger on the 



such a conception. The Anacanthini, as defined by Miiller, 

 are a purely artificial group, for the recognition of which not 

 even the excuse of external similarity can be adduced. 



A step in the right direction had already been made by 

 Cope in 1871 *, followed later by Gill and by Jordan, in 

 separating the fiat-fishes as a suborder under the Diimerilian 

 name of Ileterosomata, but merely on account of the asym- 

 metry of the skull, and, to quote from tlie latter author f, 

 persisting to consider the nearest relationship of this suborder 

 to be " probably with the Gadida^, although the developed 

 pseudobranchige and the thoracic fins indicate an early differen- 

 tiation from the Anacanthine fishes." 



Objections to this view were raised by J. T. Cunningham 

 in 1897 %, who observed : — *' It is a remarkable fact that 

 although the Pleuronectidse and Gadidge have generally been 

 considered to be so similar that they have been placed in 

 the same order Anacanthini, the structure and development 

 of the tail described above [heterocercy] occur in the flat-fish, 

 but are entirely wanting in the Gadidge. In the latter the 

 tail is permanently diphycercal, it is composed of dorsal and 

 [ ventral rays which are equal in number and size, and, in 

 fact, closely resemble the tail of the extinct Coelacanthidse. 

 There can be little doubt that even if the Gadidai cannot be 

 directly derived from the latter family, they are descended 

 from Crossopterygian Ganoids with diphycercal fails, and 

 have never passed through a heterocercal condition §. Al- 

 though the structure of the tail in the Gadidae was briefly and 

 correctly described by Alexander Agassiz in his paper on the 

 development of the tail, he did not attach sufficient import- 

 ance to it, believing that a very slight apparent up-bending 

 of the termination of the notochord showed the essential 

 similarity in the development of this type of tail witli that 

 seen in other Teleosteans. The proper classification of the 

 Anacanthini is yet to be worked out, but there can be no 

 doubt that the Gadidge and Pleuronectidae, instead of being 

 closely allied, are very remote from each other in structure 

 and descent." 



The latter conclusion had already been reached by Agassiz 

 from the study of fossils. On p. 260 of the fourth volume of 

 his * Poissons fossiles,' dealing with the curious extinct genus 

 Macrostoma (z=Amphtstius), to which 1 shall have occasion 

 to refer presently, he expresses the opinion that " L'ensemble 



* Trans. Amer. Philos. Soc. (2) xiv. 1871, p. 458. 

 .t ' Fishes of N. America,' iii. p. 2602 (1898). 

 X ' Science Progress,' (2) i. p. 498. 

 § See my remarks on this subject, further on. 



