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XLVII. — Description of Pygopterus Greenockii (Agassiz), with Notes on the Struc- 

 tural Relations of the Genera Pygopterus, Amblypterus, and Eurynotus. By 

 Ramsay H. Traquair, M.D., Demonstrator of Anatomy in the University of 

 Edinburgh. Communicated by William Turner, M.B. (Plate XLV.) 



(Read 5th March 1866.) 



Professor Agassiz, in his " Poissons Fossiles," vol. ii. p. 78, has mentioned a 

 species of Pygopterus as occurring in the carboniferous shales of Wardie, near 

 Edinburgh, and which he has named P. Greenockii, in honour of Lord Greenock, 

 the first collector of ichthyolites from that locality. He has, however, neither 

 given a figure of this species nor any description of it, beyond saying that the 

 known fragments consist of hardly anything but heads, with the anterior portion 

 of the trunk, and that the scales covering this part of the body are higher than 

 broad — a circumstance distinguishing them from the scales of all the other species 

 of the genus. 



Having for some time back collected fossils from this locality, I am enabled 

 not only to figure a complete specimen of the fish, but also to describe its struc- 

 ture a little more in detail, though there are still many points concerning which 

 more knowledge would be desirable. 



These fishes occur in elongated nodules of clay ironstone, which are almost 

 always divided by transverse fissures into a great many segments. When the 

 nodule becomes detached from its shaly matrix by the action of the sea, these 

 segments become separated and scattered ; hence the difficulty of acquiring 

 entire specimens. Heads are, however, more easily found, as the anterior extremity 

 of the fish is usually imbedded in a larger and more compact piece of ironstone 

 than those into which the rest of the nodule divides. To obtain an entire speci" 

 men, it is then necessary to find the nodule in situ, to extract it from the shale 

 piecemeal, and then carefully to split the separate pieces, which must, lastly, be 

 properly assorted and glued together. The specimens are always much crushed, 

 and often otherwise mutilated ; the body of the fish presenting sometimes nothing 

 more than a heap of disjointed scales. The texture of the ironstone is also 

 unfavourable to the complete study of the individual parts, as it is almost im- 

 possible to develope or work out the specimen beyond what is exposed by the 

 first splitting of the nodule. 



It is also very difficult to obtain a good view of the external sculpturing of 

 the scales and of the bones of the head, as these generally adhere with their 



VOL. XXIV. PART III. 9 E 



