Or the Sir act arc of Coccosteus decipiens, Ayassiz. 221 



been found aloncf with Coccosteus decipiens. lint with regard 

 to the peculiar fiat triangular bodies represented in his first 

 memoir on the sul)ject (9, tab. vi. and tab. vii,, fig. 2), I 

 liave had the privilege of examining two specimens contained 

 in the British Museum. 



In the first ])lace there is no evidence whatever that these 

 bodies belong to Coccosteus at all, any more than the supposed 

 *' Oberarm," as nothing in any way resembling them has ever 

 been seen in connection with the most perfect specimens of 

 C decipiens, the type of the genus, which the Scottish Old 

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

 expressed grave doubts (10, Supplementary Note) as to their 

 liavino- belonoed 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 

 Oracanthus, which is certainly Selachian, although some 

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

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

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

 Avith one margin convex, the other concave, truncate base, 

 and rounded lateral edges. A great part of the surface is 

 sculptured with closely-set tubercles, which are occasionally 

 irregularly 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. Trautschold 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 " ichthyodoridithe" (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, Por here are the words in which 



