92 Proceedings of the Royal Physical Society. 



vature shown by such specimens, along with the wearing 

 away of the apices, as if they had been subject to habitual 

 attrition at the bottom of the water in which their possessors 

 lived. In 1868 Messrs Hancock and Atthey returned to 

 the subject,! ^nd, reviewing the extensive series of specimens 

 in the collection of the last-named gentleman, divided them 

 into two categories — first, those with lateral curvature and 

 worn apices, and second, those in which apparently there was 

 only an antero-posterior curvature and in which the apex was 

 entire and pointed. The former set, which could also be 

 arranged in pairs, they regarded as pectoral, the latter as 

 dorsal} 



The occurrence of numerous spines of this genus in the 

 Blackband Ironstone of Borough Lee, near Edinburgh, having 

 lately induced me to inquire into the whole subject of Gyra- 

 canthics, I was surprised to find that, among the numerous 

 specimens which came under my observation from that and 

 other localities in Scotland, there was not one which was 

 bilaterally symmetrical, and which consequently could be 

 assigned to a median position. On this subject I published 

 a few remarks in the Geological Magazine for December 

 1882. To pursue the subject further it was, however, abso- 



1 Aim. & Mag. Nat. Hist. (4), 186^, vol. i., ]). 368. In a footnote Messrs 

 Hancock and Atthey refer to a paper by Messrs Atthey and Kirkhy, 

 entitled " Fish -remains in the Coal-measures of Durham and Northumber- 

 land," as having been read before the British Association at Newcastle in 

 1863, and as containing the first suggestion of the paired nature of these 

 spines. I cannot find this paper in the British Association's Proceedings 

 for that year ; and although a paper of the same title is found in the 

 Proceedings of the Tyneside Naturalists' Field Club, it contains no reference 

 to Gyracanthus. These original remarks would therefore seem not to have 

 been published. 



^ In a paper on Tristychius, published in the Ann. & Mag. Nat. Hist, for 

 September 1883, Mr. T. Stock states, with regard to Messrs Hancock and 

 Atthey 's views as to the pectoral nature of certain GyracantJms-s-pmes, that 

 he has "been able to confirm their conclusions by the finding of an interest- 

 ing specimen containiug well-preserved remains of the pectoral arch," and 

 refers to a paper on the subject, read by himself to the Edinburgh Naturalists' 

 Field Club. However, on consulting the paper, now published (Trans. 

 Edinb. Nat. Field Club, vol. 1., i)t. 2, pp. 50, 51), it turns out that the 

 ** pectoral arch," in this case, is Messrs Hancock and Atthey's "carpal bone," 

 of which more anon. 



