312 THE PEOCEEDINGS OF THE LINNEAN SOCIETY 



little behind the transverse band mentioned above, and extends 

 along the middle of the back to near the first dorsal, when it 

 divides and forms a band on each side, extending to and on the 

 ' ventral fins. On that part of this black band which lies exactly 

 between the postenor part of the base of the first dorsal and 

 pectoral fins there is a concave curve, and from that point a 

 black band extends to the pectoral fin. There is also another 

 black band anterior to this, which extends from the first band in 

 front of the first dorsal fin, and joins the second band on the 

 pectoral ; this band is a little curved (the concavity forwards), 

 and forms with the other bands a small enclosed light-coloured 

 triangular space. Another broad dark band extends along the 

 back from the base of the first dorsal, and on each side of the 

 second dorsal, to the tail. There is a lateral line along the body 

 and tail, marking rather distinctly the line of demarcation be- 

 tween the dark colour of the back and the light colour of the 

 belly. Both the dorsal fins and the anal are rather light-coloured, 

 the caudal is darker, and the pectorals and ventrals are blackish 

 above, and pinkish below and on the edges. 



In specimens preserved in spirits, or dried, these markings en- 

 tirely disappear, and they are never so vividly marked in adult 

 specimens as in the young, as will be seen by reference to the 

 very young specimen figured in plates 22 and 23, 



The average size of the adult of both sexes is a little over 

 three feet, and they seldom, if ever, attain a length of four feet. 

 As the relative size of the difierent parts has been rendered with 

 the greatest exactness in the accompanying plates, along with an 

 accurate scale, I do not think it necessary to give a series of 

 measurements. 



The sexes scarcely difier in size or marking. The egg case is 

 large (six inches long), conical, of a tough dark brown coriaceous 

 texture, with six revolutions of a similar material spirally wound 

 round it, forming a broadly-flanged conical screw. A good figure 

 of it is given in Dumeril's Hist. Nat. des Poiss. vol. 2, pi. 8, 

 figs. 2-3, but that author was not then certain that it was the 

 egg of a Heterodoukcs. 



