4 Br. R. H. Traquair — On a JSFew Fossil Shark — 



Measurements. 



Entire length ' _. 28 inclies 



Length from tip of snout to inserted root of first dorsal spine ... 7 J ,, 



,, „ ,, ;j second ,, ... 16 ,, 



,, ,, commencement of lower lobe of caudal fin 24 ,, 



Depth at exsertion of first dorsal spine ... ... ... ... 5 „ 



,, ,, second ,, 4 ,, 



,, commencement of lower lobe of caudal fin ... ... I5 ,, 



As the upper lobe of the caudal fin is, before its termination, 

 unfortunately cut off by the edge of the slab, the length of the fish 

 must have been originally somewhat greater. 



Bead. — Although the fish lies on its side as far as the shoulder, 

 the head appears to be so twisted as to turn up the lower surface 

 obliquely. It is impossible to give any anatomical description of 

 the head, as it consists of calcified cartilage so crushed as to render 

 the reading of its parts rather unsafe. It is, however, clear that the 

 snout was blunt, and I think also that the mouth was nearly terminal, 

 as in the recent Cestracion. Unfortunately, the dentition is not well 

 shown. There are several traces of teeth, but only one is exhibited 

 in any degree of completeness. This consists of a smooth, pointed 

 conical cusp (Fig. 6), supported on a broadish base, the entire height 

 being |- of an inch. The lateral extremities of the base are not 

 well seen : it looks as if it might support lateral denticles, but it is 

 dangerous to attempt to develope it further. So rare are the oppor- 

 tunities for correlating the teeth and spines of Palseozoic Selachii, 

 that it is indeed disappointing to find so little of the former shown 

 in the present specimen. But the Cladodont nature of this one tooth 

 seems undoubted, and that is an important point gained. 



Body. — The body of the fish is composed of a greyish-yellow or 

 dirty cream-coloured mass. On examining it carefully, three sets of 

 things are seen : — 



1. Shagreen granules or "placoid scales" (Fig. 7). These are 

 minute, aV to -J^j inch in diameter, mostly delicately ridged and 

 pectinated, though sometimes they appear smooth. Some evidence 

 of a lateral line is seen on the hinder part of the fish, below and 

 behind the second dorsal spine. 



2. Masses of a dirty yellowish-white material, evidently internal 

 in position to the shagreen granules. Seen under a lens, this mate- 

 rial has a fibrous aspect, the fibres running, in almost every case, 

 parallel with the axis of the fish. It is also divided across by some- 

 what oblique parallel lines or septa, usually about ^ inch apart. 

 For instance, just behind the scapular arch, six such septa are seen, 

 and the same appearance is also well shown between the two spines 

 near the dorsal margin, when in front of the second spine they also 

 present an appearance of zigzag curvature. Can this substance be 

 other than the fossilized body-muscle of the fish ? And it is certainly 

 interesting that my friend, Mr. B. N. Peach, has also discovered 

 muscular fibre in the interior of the limb-joints of fossil Scorpions 

 from the same deposits. 



3. Passing through the body of the fish in an irregular curved line, 

 and evidently imbedded in the fossilized muscular substance, is a 



