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seen, as indicated in the figure, a fiat liony rim; the illustraticn also clearly 

 demonstrates the peculiar form of one of the lateral surfaces. 



The posterior surface is concave and possesses especially at the top a 

 great number of narrow, flat bony frames, closely fitting into the rising 

 grooves or ruts that mark the central fore-part of the os frontale. 



The inner surface, in conclusion, by which the two nasalia are adpressed 

 together, is even and, save a few unimportant irregularities, they do not 

 display any special features. 



The zygomaticum (fig. 2 and 3) is missing in many whale-skeletons and 

 is very rarely reproduced or even included in the illustrations as a part of 

 the skull; in the latter case the peculiar forms are not sufficiently emphasised, 

 owing to the reproduction being on too small a scale. 



The zygomaticum of our Buitenzorg skeleton however, appears to me 

 to be dissimilar in structure when compared with that of other Balaenoptera- 

 skeletons it is therefore that the following description has been supplemented 

 with two illustrations clearly picturing the under- and the upper surface of the 

 zygomaticum (jugal arch). It is a curved bone of 541/2 ^•^- •'i length, forming 

 the bony lower wall of the orbit which narrows down funnel-shaped towards 

 the interior. At the back it shows a more or less rounded part, small in 

 proportion to the whole length of the bone, serving to effect the articulation 

 with the tapering outer extremity of the squamosum which is produced forward. 

 Anteriorly it possesses a heavier and broadened part with rough bone- surfaces 

 which for the purpose of articulation are inserted between the backwardly 

 produced outer prominence if the upper maxillary and the angular part of 

 the OS frontale which is directed outwards and forwards. 



This anterior part of the zygomatic arch is however nothing else but 

 the OS lacrymale coalescent with the zygomaticum. 



The tympanicum (fig. 4) is a more or less rounded bone measuring 

 13 c.M. in length. It displays a very peculiar structure and consists of a very 

 hard compact mass of bone, so that unlike the rest of the skeleton it is 

 exceptionally heavy. 



The peculiar plicae and curves in the surface of the bone are hard to 

 describe but are sufficiently marked in the figure representing the left ear- 

 bone viewed from the side turned to the os temporale. This side shows an 

 elongated aperture and a very thin, interrupted bony rim by which the 



