IX. Note on the Spines of Gyracanthus

Abstract

In the works of Agassiz, Buckland, De la Beche, and others, the spines of the genus Gyracanthus have been described as dorsal. Several years ago I had the pleasure of examining the finest collection of these Ichthyodorulites I have yet seen, collected by Mr. Thomas Athey, near Newcastle-on-Tyne. He drew my attention to their form; they were all more or less laterally incurved, and shaved away near the apex. He remarked that he was inclined to think that they were lateral,1 and not dorsal spines, and requested me to examine those found in our Scottish beds. This I have done in all the public and private collections I have had access to, and have found that they occur most plentifully in a similar position in the strata, but they are all more or less similarly incurved and shaved away at the apex. If they were dorsal, I would naturally expect to find them, if not straight, curved backwards. This, however, I in no instance found.2 If we examine any of the recent fish that have spines— Acanthus vulgaris and Trigla Gurnardus , we find that the former shows dorsal, the latter dorsal, pectoral, and ventral spines. Of the former I have examined several hundreds within the last few years, and find that both the anterior and posterior spines are worn away at the apex, but always on the anterior face. In all instances I found the anterior spines more worn away than the posterior, showing plainly that when the fish was swimming This 250-word extract was created in the absence of an abstract