Structure of Coccosteus decipiens, Agassiz. 133 



Coccosteus decipiens in all conditions of preservation and from 

 all the beds and localities of the Scottish Old Red Sandstone 

 which have yielded such remains, including the collections in 

 the British Museum, in the Museum of Practical Geology, in 

 the Edinburgh Museum of Science and Art, the Gordon- 

 Cumming collection at Forres, and many others, but without 

 meeting with any other parts either of endo- or exoskeleton 

 than those I have described. And, in particular, I have not 

 seen the smallest evidence of the presence of any pectoral 

 limb, nor any trace of an articular surface on any of the 

 bones to which such a limb could have been articulated. It 

 can scarcely be believed that had such a limb been present it 

 would either have escaped preservation or observation in so 

 large a number of specimens. Nevertheless more than one 

 author has been disposed to believe in the presence of such a 

 limb in Coccosteus. 



In the restored figure of Coccosteus given by Hugh Miller 

 in the first edition of the ' Old Red Sandstone ' (2, pi. iii.) no 

 limb is represented, and its absence is positively affirmed in 

 the text. But in subsequent editions, and also in Duff's 

 ' Geology of Moray ' (3, pi. viii. fig. 1), a peculiar " paddle- 

 shaped " body is represented appended to the head. How- 

 ever, Hugh Miller, in a footnote, explains that he has ascer- 

 tained that the supposed arms " were simply plates of a pecu- 

 liar form." Of course there is not the smallest doubt that the 

 idea of this limb owed its origin to a displaced maxillary bone. 



But more recently, in connexion with what appear un- 

 doubtedly to be fragments of a large and peculiar form of 

 Coccosteus, Trautschold (9 and 11) has described and figured 

 from the Old Red Sandstone of Russia certain peculiar bodies, 

 which he considers, though not without doubt, to appertain 

 to supposed large arms or " Ruderorgane " belonging to that 

 species, which he accordingly names Coccosteus megalopteryx. 

 What the fragments are to which he applies the term " Ober- 

 arm " I have not the slightest idea, as I have not seen them, 

 and certainly nothing like them has ever been found along 

 with Coccosteus decipiens. But with regard to the peculiar 

 flat triangular bodies represented in his first memoir on the 

 subject (9, tab. vi. and tab. vii. fig. 2), I have had the privi- 

 lege of examining two specimens contained in the British 

 Museum. 



In the first place 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 connexion with the most perfect specimens of C. 

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



