88 bulletin: museum of comparative zoology. 



" Des museaux excessivement longs, tels que nous les trouvons chez Eurhino- 

 delphis, Cyrtodelphis, Aerodelphis, Inia, Pontoporia et Platanista, paraissent etre 

 pa*rticuliers aux animaux fluviatiles, ou plus precisenient, a ceux qui se servent de 

 l'extremite du museau pour fouiller la vase et en faire sortir la nourriture minis- 

 cule qui y grouille tout corame chez les oiseaux a long bee (herons, cigognes, 

 becasses, etc.), oiseaux de marais et de rivages, dont le bee est, physiologiquement, 

 non morphologiquement, identique aux longs rostres des dauphins fluviatiles. Le 

 bee d'une becasse est entierement analogue au rostre de Pontoporia." 



Enough has now been said by way of emphasizing the purely adaptive 

 feature presented by the elongated rostrum of most Miocene Iniinae (Iniidae of 

 Gill). Therefore, notwithstanding the marked difference in this respect which is 

 exhibited by Lophocetus, we may still place all these forms in close association 

 with the typical existing genus on account of mutual resemblances in other 

 respects. It is unnecessary to enumerate here the various points of agreement 

 that have been observed between Inia and leading longirostrate forms like Champ- 

 sodelphis and Schizodelphis ; for particulars one may refer to Abel's memoir of 

 1899, already several times quoted. These two genera, according to this author 

 (p. 868), are very intimately related to Inia, but on the other hand Saurodelphis 

 and Eurhmodelphis are more distantly related, and belong probably to a different 

 evolutionary series. Accepting this conclusion, it is interesting to note that Loph- 

 ocetus displays rather close resemblances to the two first-named genera, and also to 

 Aerodelphis in the restricted sense that the term is now understood by its author. 

 Yet there is even closer affinity between Lophocetus and Inia itself. Schizodel- 

 phis and Eurhmodelphis are to be regarded as more primitive than the form we 

 are considering, and more primitive also than modern Iniinae, in that the frontals 

 take part to a considerable extent in forming the gently rounded summit of the 

 cranium, where they are freely exposed, and are either wholly or partly separated 

 from each other by the interparietal. But in Lophocetus the interparietal, which 

 is fused with the steeply inclined supraoccipital, barely excludes the frontals from 

 meeting in the middle line at the vertex of the cranium. Needless to say, too, 

 that the disposition of the parietals in Lophocetus differs radically from that 

 observed in Saurodelphis, where they retain more nearly their primitive arrange- 

 ment and are in contact with each other in the median line. But as compared 

 with Schizodelphis, the large extent of the parietal surface, the high vertical walls 

 formed by these bones, and their powerful crests for the attachment of jaw muscles, 

 show considerable likeness, and it is only in the more primitive arrangement of 

 the frontals that this portion of the cranium differs very conspicuously in the two 

 genera. 



Neither Lophocetus nor any of the best known longirostrate genera resemble 

 Eurhmodelphis in having such highly specialized characters as a completely 

 closed temporal fossa and greatly thickened supraorbital ridges. Closed temporal 

 fossae are the rule among Dolphins proper, Ziphioids, and the Physeteridae, but 

 occur only exceptionally among fossil Platanistids. Like Eurhmodelphis, how- 

 ever, but unlike Inia and Iniopsis, there is no swelling or thickening of the pre- 



