116 Part III. — Twenty-sixth Annual Report 



XVI. Number op Kays in the Unpaired Fins. 

 See Table, p. 109. 



XVII. Number op Vertebra. 

 See Table, p. 1 09. 



XVIII. Number of the Vertebra bearing the First Haemal Arch 

 See Table, p. 109. 



XIX. The Colour op the Inside op the Mouth : — 



The inside of the mouth is black in pollachius. 



,, „ „ dark, bluish tinge, in virens. 



„ „ „ brown in ogac. 



„ ,, ,, white in callarias, merlangus, poutassou, 



seglefinus, luscus, minutus, argenteus, 

 esmarki, saida (dull colour in spirit), 

 navaga (yellowish in spirit). 



XX. The Abdominal Cavity : — 



The Colour of the Peritoneum : 



Peritoneum steel-grey colour callarias. 



„ black seglefinus, argenteus, poutassou, saida, 



esmarki. 



„ dark merlangus, saida, ogac. 



„ white pollachius, virens. 



The First H^mal Arch. 



The number of the vertebra bearing the first hsemal arch varies with 

 the species, as will be seen on reference to the table on page 109. 



There is a marked difference in the shape of the first hsemal arch in 

 different species. This is exhibited both in the size of the arch and also 

 in its shape. Drawings of this bone for all the species, with the exception 

 of G. ogac and G. navaga, are shown in Plate IV. The posterior side of 

 the arch is represented, the vertebra resting on its anterior disc. 



The arch may be round as in pollachius, fig. 39, or nearly round, the 

 condition found in merlangus, fig. 65. The most common shape is that 

 of a broad oval, and that form is found in callarias, fig. 61 ; virens, fig. 66 ; 

 minutus, fig. 63 ; luscus, fig. 67 ; saida, fig. 59 ; and esmarki, fig. 64. 

 ^glefinus, fig. 68 ; poutassou, fig. 57 ; and argenteus, fig. 58, have a 

 narrow, oval arch. 



iEglefinus is readily distinguished from the other species by its 

 characteristic first hsemal arch. It bears two lateral wing-like expan- 

 sions, fig. 68, which have no counterpart in the other species. 



This wing-like expansion is repeated on the second arch, but it has 

 disappeared on the third, a thickened ridge alone representing it. These 

 lateral plates receive the ends of the swim-bladder. Sometimes the 

 expansions are found on three of the 20-23 vertebrae. The first 

 hsemal arch in this species is most commonly found on the 22nd vertebra, 

 but it is also found on the 21st. It may happen that the arch is not 

 complete, one side being short, although the other side may be continued 

 downwards into the hsemal spine. If the hsemal spine is present on an 

 imperfect arch, this is regarded as the first hsemal arch ; but if the spine 

 is absent and the arch incomplete, it has been neglected. 



Facultative Htemal Arch. — Occasionally a facultative hsemal arch is 

 formed by the union of the ribs of the vertebra immediately preceding 

 the first hsemal arch. In these cases there is no hsemal spine. Such an 



