134 Dr. R. H. Traquair on the 



Sandstone has afforded. Prof. v. Koenen has also expressed 

 grave doubts (10, supplementary note) as to their having 

 belonged to Coccosteus, though he thinks it not impossible 

 that the piece referred to as " Oberarm " may be identical 

 with the " stabformiges Ruderorgan," the existence of which 

 he himself maintains. 



In the second place it seems to me highly probable that 

 they are Selachian appendages; indeed, their form and 

 appearance is strongly suggestive of an affinity with Ora- 

 canthus, which is certainly Selachian, although some years 

 ago Mr. J. W. Davis was inclined to refer it to the Placo- 

 dermi, though not as a pectoral limb. These so-called 

 " Flossen " are flat bodies, of a horn-shaped outline, pointed, 

 with one margin convex, the other concave, truncate base, and 

 rounded lateral edges. A great part of the surface is sculp- 

 tured with closely-set tubercles, which are occasionally irregu- 

 larly elongated, and all with stellate bases ; these tubercles 

 being an integral part of the substance of the appendage, 

 the term " Schuppenhaut " applied to them by Prof. Traut- 

 schold seems hardly appropriate. The basal margin of the 

 body is not tuberculated but striated, and this striated portion 

 extends further up on one side than on the other. 



Now, Prof. Trautschold admits (11, p. 36, note) that the 

 body figured by Pander as an " ich thy odor ulithe'" (6, pi. vii. 

 fig. 22) is identical with the end of one of the supposed 

 " fins " of Coccosteus megalopteryx ; and if so, then its micro- 

 scopic structure is not that of a Coccostean bone, but of a 

 Selachian appendage. For here are the words in which 

 Pander refers to the body in question : — " Fig. 22. Ein 

 Ichthyodorulithe, mit ausgezeichnet schonen Sternen auf beiden 

 Flachen und Kanten. Die Sternchen sind ausserlich von 

 denen von Asterolepis, Coccosteus und Homosteus unmoglich 

 zu unterscheiden, aber die microscopische Structur ist ganz 

 verschieden. Knochenhohlen fehlen ganzlich. Die Tuberkel 

 bestehen aus wahrer Dentine und die ganz innere Masse aus 

 einem Gewebe von Markcanalen, umgeben von concentrischen 

 Kreisen, in der Grundsubstanz, welche von den nach alien 

 Seiten ausstrahlenden feinen Zahnrohrchen unter rechten 

 Winkeln clurchschnitten werden " (6, pp. 102, 103). From 

 this description, along with Pander's figure of the microscopic 

 structure (ib. fig. 34), the true nature of these bodies is, I 

 think, pretty evident. 



1 am therefore quite unable to accept Prof. Trautschold's 

 views as to the " fins " of Coccosteus. 



But, as already mentioned, Prof, von Koenen has affirmed 

 the presence in Coccosteus of a " Ruderorgan/' and in his re- 



