6-1 Dr. E. n. Traquair — Fish-remains from Borough Lee. 



II. — Notice of New Fish Eemains frobi the Blackbanu Iron- 

 stone OF Borough Lee, near Edinburgh. No. V. 

 By Dr. R. H. Trauuair, F.R.S. 

 Aganacanthus striatulus, n. gen. et sp. 



I HAVE recently obtained from the Borough Lee Ironstone 

 several specimens of a Selachian spine, apparently new, and 

 showing several features of a very interesting character. 



The most perfect of these specimens measures 5^ inches in length ; 

 but as the apex is broken off, its original length was probably six 

 inches. In general form it is stout and rapidly tapering; its circum- 

 ference at the thickest part, two inches from the proximal extremity, 

 being 3| inches, and only -^^ inch where it is broken off distally. 

 The spine shows, moreover, a pretty strong antero- posterior curva- 

 ture, besides which, it is also slightly bent laterally, there being no 

 indication that this lateral curvature is in any way the result of. 

 distortion by pressure. The base is occupied by an extensive cavity, 

 which extends along the back of the spine as a deep open hollow or 

 sulcus, which closes externally at a distance of S-^V inches from the 

 proximal extremity. Transverse sections show that this cavity, after 

 its external closure on the posterior aspect, of the spine, becomes 

 internally very soon obliterated. 



The anterior margin is rounded, and from it two sides diverge 

 backwards, each of which, in the proximal part of the spine, becomes 

 rounded off posteriorly into the corresponding lip of the posterior 

 hollow or sulcus. But one of these sides, that on the concave aspect 

 of the spine, is narrower than the other, so that the opening of the 

 aforesaid hollow does not look right backwards; accordingly this 

 hollow is visible when the spine is looked at from one side, invisible 

 when viewed from the other. After the closure of the sulcus the 

 transverse section assumes a trigonal aspect, with rounded angles, 

 but the two sides, corresponding to the lateral aspects of the spine, 

 remain as before unsymmetrical, one being (in section) longer than 

 the other. Where the point is broken off, the posterior side, which at 

 at first was flattened, has now become slightly convex; but the angles 

 between it and the two unsymmetrical lateral surfaces are still evident. 



The external surface shows no trace of enamel, nor any sort of 

 sculpture save a close and delicate longitudinal striation, which 

 gives it that so-called "fibrous" appearance characteristic of the 

 implanted portions of other fossil shark-spines. 



Another specimen measures 5* inches in length, and displays the 

 same essential characters as the preceding, save that it presents no 

 lateral curvature, and that its point, which has certainly not been 

 lost by breakage, in getting it out of the stone, seems obliquely 

 sliced, or worn, off posteriorly. But another interesting point is 

 that this specimen is asymmetrical in precisely the opposite direction 

 to the preceding. Place the two spines together on a table with 

 their backs facing each other, and the posterior hollows of both are 

 visible; reverse them, so that the anterior margins ai'e opposite, 

 and in both cases the posterior hollows are invisible. It is therefore 



