174 TRANSACTIONS OF THE AMERICAN PHILOSOPHICAL SOCIETY 



in favor of this conclusion and then goes on (1903-1906, pp. 214, 215) to give a careful and 

 judicious evaluation of the craniological resemblances and differences between the mor- 

 myroids and the Albulidae, to which the interested reader is referred. Consequently it 

 cannot be said that the point of origin of the whole mormyroid series from primitive Cre- 

 taceous isospondyls has been determined with any degree of certainty, since they share 

 important characters with such diverse families as the Albulidae and Clupeidae. The 

 otoliths of mormyroids, as noted by Frost (1925, p. 160), are highly peculiar. The saccular 

 otolith (sagitta) is small and ill-formed, while the asteriscus and lapillus are unusually large. 

 In the sagitta the sulcus widens out behind and is large and rounded posteriorly; in this 

 and certain other features the sagitta resembles that of Osteoglossum, but Frost does not 

 place much value on this resemblance; he concludes (p. 162) that a comparison of the oto- 

 liths suggests that the Mormyridse represent a highly specialized group, and that, so far as 

 the otoliths are concerned, they have little in common with the remainder of the Isospondyli. 



"Concerning the genera Notopterus and Hyodon" concludes Ridewood (1904c, p. 214), 

 "there is but little to be said, except that the latter possesses a greater proportion of 

 primitive characters. Of the forms described in the present paper, there can be little doubt 

 that the Mormyridse are the most specialized, and Hyodon the least specialized; but the 

 close study of the skulls of these fishes does not lend support to a view of relationship 

 recently expressed by Boulenger. On page 116 of his book ' Les Poissons du Bassin du 

 Congo,'' \9Q\[b\, he writes: — '^ Les Notopterides me semblent occuper vis-a-vis des Hyodontides 

 une position analogue a celle qu^occupent les Mormyrides vis-cL-vis des Albulides, c'est d dire 

 qu'ils peuvenl en etre consideres comme modification excentrique.' In considering the possi- 

 bility of evolution of the Notopteridse from the ancestral Hyodon, one must not lose sight 

 of the fact that Notopterus — in the presence of the large lateral cranial foramen bounded 

 by the squamosal, epiotic and exoccipital, in the attempt (a futile one, it is true) of the 

 thin scale-like supratemporal to cover it, and in the presence of a paired tendon-bone of 

 considerable size projecting down from the side of the second basibrancTiial — exhibits 

 characters strikingly constant in the Mormyridse, but not possessed by Hyodon. 



"Although in both Notopterus and Hyodon there are vesicles of the swim-bladder on 

 the lateral face of the otic region of the cranium, it does not necessarily follow that these 

 structures have had a common origin. The connection between the swim-bladder and the 

 ear must not be relied upon too implicitly as indicating close relationship between such 

 fishes as possess it. That it has arisen independently in different groups is evident from the 

 remarkable difference between the methods by which the result is arrived at. Compare, 

 for instance, Clupea on the one hand and the Ostariophysi on the other. Stannius (Handb. 

 d. Anat. d. Wirbelth., i, p. 2) mentions that there is a connection between the swim-bladder 

 and the ear in the Macruridse among the Anacanthini, and in the Berycidse and Gerridse 

 among the Acanthopteri; while Sagemehl (Morph. Jahrb., x, 1885, p. 5.1, footnote) observes 

 that it occurs in the Gadidoids Physiculus and Uralepius, and in the Scleroderm Balisies" 

 (1904c, p. 215). This passage, I think, offers a sufficient answer to the recently expressed 

 views of Garstang (1932) concerning the supposed relationship of the mormyroids and 

 other isospondyl "Otophysi" to the Ostariophysi. 



Thus Ridewood's detailed analysis of the craniological characters of the families of 

 malacopterygian fishes has revealed the great extent and complexity of the phylogenetic 

 problem and contributed greatly to clarify the issues and distinguish the well established 



