CiOR MK. It. II. wiiiTEiruusE OK THE [Apr. 5, 



Clenend reiiKirks on the Percesoces. 



This Ku])-onlei' presents considerable diversity in caud.al liu 

 structure ; Atherina, with its free urostyle and numerous hypurals 

 attached to it, possesses a comparatively lowly specialized caudal, 

 while that of Mngil is quite a specialized form. Arranged in 

 ascending order of honiocercy, the four genera will appear thus : 

 Atherina, Ammodi/lea, Belone. Miir/il, which arrangement does not 

 correspond with that of general classification. 



A N A C A N T H I X I. 



Macrvruhr. — The fishes in this family possess no caudal fin ; 

 thev are deep-sea forms and the body ends in a finelv tapering 

 tail". 



MoLVA VULGARIS. (Gadidiv.) (Plate XLIX. fig. 17.) 



The Ling possesses a simple type of Gadoid tail. No less than 

 thirteen vertebrpe contribute towards the support of the caudal fin ; 

 all of the.se vertebrse aie pi^ovided with hypural bones {hy.) and 

 all, except the last two, with epural bones too; special attention, 

 therefore, need be directed only to parts connected with these 

 last two vertebrae. The final vertebra possesses no nrostyle, 

 and is firndy fused with the broad last hypural which occupies 

 a. terminal position and bears five dermotiicliia. That part of 

 the last hypural which encroaches upon the dorsal side of the 

 last centrum is seen in other Gadida\ e. g. 6'. minutus, to be a 

 secondary extension of this bone, only appearing late in develop- 

 ment ; in voung stages the hypural is totally ventral to the 

 centrum. The hypural bone of the penultimate vertebra is also 

 broadly expanded and bears three fin-rays. Between this hypui-al 

 and the next anterior one is a ventral caudal radial (v.c.;-.), in no 

 w^ay fused with any other skeletal element. Most of the hypural 

 bones show signs of being fox-med by the coalescence of haemal 

 arch and radial, the line of fusion being specially prominent after 

 clearing agents have been used ; the shading in the figure is 

 intended to show this. 



Epaxially, it is interesting to note the great reduction of the 

 neural arch of the penultimate vertebra; that of the ante})enul- 

 timat(! contributes to the formation of an epural bone. Between 

 this la.st e])ural and the dorsal side of the la.st hypural are two 

 dorsal caudal ratlials, each bearing a fin-ray ; these radials never 

 fu.se with the neural arch, but always remain jierfectly free. It 

 will thus 1)6 seen that tlie caudal fin of Molra is not .symmetrical 

 internally and that the hypaxial fin-rays outnumber the epaxial ; 

 it is in every way consistent with homocercy, ^nd its terminal 

 skeleton with a very highly specialized type of homocercy. 



Gadiculus ARGErifTATUS. (Gadidfc.) (Plate XLIX. fig. 18.) 

 This small Gadoid posses.ses a more generalized caudal fin than 

 does the preceding type; this is due solely to the presence of a 



