of the Fishery Board for Scotland. 



341 



the battens in a lateen sail have to the sail. The postdavide is 

 present in the Plaice-, Halibut-, Citharus-, and Turbot-groups, but 

 was not found in any of the species of Soleidse examined. Cunningham 

 in his " Treatise on the Sole " does not say whether this bone is present 

 or absent. 



Along the internal border of the posterior concave aspect of the 

 clavicle, the plate of cartilage which gives rise to the scapula and 

 coracoid is attached. The configuration of these two bones is very 

 similar in all the groups. In the Turbot, only the central portion of 

 the upper plate has become ossified to form the scapula. All around it 

 is cartilaginous, even the "brachial ossicles" and the base of the pectoral 

 fin. The degree of ossification is greater on the external surface of 

 these bones, and is greater on the upper or eyed side of the body than 

 on the under. In the Plaice- and Halibut -groups the scapula and 

 coracoid are firmly ossified and fused together. 



The coracoid extends downward in a long styliform process which is 

 free and cartilaginous at its lower end. The relation of this process to 

 the davide is sometimes of great importance in the classification of the 

 Teleostei, but in very few groups of the flat-fishes was any great change 

 noticed. Sometimes the styliform process is broadened out as in 

 Citharus (Fig. 21) and the Soles (Fig. 24), sometimes it seems to be 

 absent, and in a few species of Soles and in Tephritis it was found to be 

 attached all along its edge to the davide. 



The bones which have been mentioned do not display any differences 

 that seem of importance for the purposes of classification, though 

 presenting many variations in details. The case is different with the 

 pubic bones and position of the ventral fins. The pubic arises from the 

 lower posterior surface of the clavicle, and may be divided for the purpose 

 of description into two portions. The portion leading down from the 

 clavicle is club-shaped, and of very varying length in different species. 

 It ends inferiorly in a sharp-pointed spine (s., Figs. 18, 19), which is of 

 more frequent occurrence in the Plaice- and Halibut-groups than in the 

 Turbot-group. From the lower third of this club-shaped bone arises 

 anteriorly a thin triangular lamina (l.p.). Sometimes the difference 

 between these two portions of the pubic bone is not well marked, as in 

 the Sole -group and individual species of the other groups, but it is con- 

 venient to make the distinction. In addition to these two portions there 

 is a third which takes the form of lateral wings near the line where the 

 laminar portion arises. They are prominent in the Turbot (Fig. 19, s.p.), 

 in the Plaice they are compressed alongside the laminar portion 

 (Fig. 18, s.p.), but in many species they are quite absent. These minor 

 differences are, however, insignificant in comparison with the changes 

 in the position of the pubic bones relative to one another. In the 

 Plaice- and Halibut-groups the jmbics run parallel along their whole 

 length. This is also the case in the Sole-group when the ventral fins 

 are symmetrical. In the Turbot-group we find that the club-shaped 

 portion of the pubic of the under or blind side tends to lie behind that 

 of the upper or eyed side. In Arnoglossus (Fig. 23) the cliange is not so 

 marked, but in the Megrim, Topknots, and Turbot the former lies com- 

 pletely behind the latter. In Citharus we have a transition to whit is 

 found in Arnoglossus, the club-shaped portion of the pubic bone of the 

 eyed side being only slightly anterior to that of the blind side (Figs. 21 

 and 22). 



These differences with regard to the position of the club-shaped 

 portions of the pubic bones are accompanied by differences in the 

 structure and position of the laminar portions. In the Plaice- and 

 Halibut-groups these lie wholly behind the base of the clavides, to which 



