BKOTULOinS. 145 



strengtliened, the rays being bound together to form .a broad rigid oar tliat 

 must be of great advantage in making a sudden dasli forward and upward 

 (see Plate XXXV., fig. 1, also figs. 2 and 3 showing the jji'ocesses for attach- 

 ment of the muscles controlling the rajs). 



Quite generally the membranes of the dorsal and the anal fins are contin- 

 uous with the membrane of the caudal fin ; examination of the type proves 

 Barathrodemus mauatinus of Goode and Bean to be no exception to this. 



On some of the genera the eyes are comparatively large ; on others they 

 are small ; and on a few they are rudimentary or absent, as on Aphyonus, 

 Typhlonus, and Sciadonus (Plate F, fig. 4). The peculiar conditions appar- 

 ent on Leucicorus, Plate XXXVIII., probably indicate deterioration and loss 

 later in life of an eye that in the earlier stages of the individual may have 

 been serviceable and normal. 



The Lateral System is well developed on the head; frequently it is im- 

 perfect or absent behind the body cavity ; in cases it appears to be absent 

 from the entire body, and in others, as on Porogadus, several lines of the 

 system are to be seen immediately behind the head. Because of the promi- 

 nence of the cephalic portion of the sj'stem in all the members of the group 

 it has been studied on a number of the genera and species for compari- 

 sons in regard to derivations and affinities, Plates LXXV-LXXXI. From 

 these the comparisons have been extended to various other groups near and re- 

 mote. No doubt the system, in addition to its sensory function among shoal 

 water types, has become luminous, and possibly in cases electric, at greater 

 depths. The peculiar disks in the canals, haidly to be detected in those of 

 the shoals, attain much greater development on the bathybial species and, in 

 po.sition and arrangement clearly indicating genetic relationship through 

 common ancestry, are similar in families that in our systematic arrange- 

 ments are widely separated. Compare, for instance, the Berycoids, Plate 

 LXXII., with the Brotuloids, Plates LXXV., or the Macruroids, Plates 

 LXXXIIL, LXXXIV. The affinities of closely allied species are to be seen 

 in comparing the figures of Plate LXXV. with the figures of Plate LXXVI. 

 In a couple of the species the nerves have been traced from the disks to 

 the brain and from the brain to the disks, Plate LXXVIII. The com- 

 plicated distribution of the nerves and vessels in the disks and between 

 them is shown on Plate XXXV., fig. 4, Plate XXXVIIL, fig. 7, and Plate 

 XXXIX., fiff. 2. 



