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Gloser examination of the ridges on the body shows, that those marked with 

 sd and cl belong to parts of the inner skeleton, namely, to the supraclavicle and 

 clavicle respectively, and that the remainder belong to some peculiarly modified, 

 large scales: these taken together correspond to the armour in Amphisile. Just as 

 in the latter the cuirass belonged in reality only to the trunk, we find that the 

 condition is the same in Centriscus; but it is easier to recognise in the latter, 

 where the disproportion between the fore-trunk and the rest of the fish is less 

 obvious than in Amphisile. hi describing the exoskeleton of Centriscus we must 

 distinguish between (1) the armour on the trunk or thorax and (2) the true scales. 



(1) The thoracic armour makes its presence felt as soon as we take the 

 fish in the hands; in fact, it makes the anterior part of the fish quite stiff and 

 immovable. It is therefore so much the more remarkable, that this has hitherto 

 been but little observed and never, so far as I know, compared closely with the 

 condition in Amphisile. This may be due partly to the fact, that the large scales, 

 of which it is composed, are more or less hidden by scales of the ordinary type, 

 which cover them to a greater or less extent, in some specimens more than in 

 others. The thoracic armour here also consists of a dorsal and a ventral part. 



When the covering scales are removed, the dorsal armour is seen, as in 

 Amphisile, to be composed on each side of two rows of plates, an upper, dorsal, 

 and a lower, lateral (PI. I, fig. 3). The upper consists of 3 members, connected 

 with one another by dentate sutures and likewise with the anterior 3 of the lower 

 row; their upper margin does not reach to the middle line of the back and thus, 

 in contrast to Amphisile, they do not meet the corresponding plates from the op- 

 posite side. The posterior and largest is closely attached at its upper point with 

 a part of the upper end of the interspinous bone for the small, first spinous ray 

 of the dorsal fin (R', PI. I, fig. 3). 



The lower row consists of 5 plates (PI. I, fig. 3 and text-fig. 23, / — V), firmly 

 connected with one another by dentate sutures where they meet; two oblong 

 interspaces covered by ordinary scales are found between the first three plates and 

 the upper row; a similarly scaled, narrow interspace, opening upwards and back- 

 wards, separates the two posterior, much smaller plates from the last plate of the 

 upper row. The outer surface of all the plates of the dorsal armour is provided 

 with strong, finely toothed ridges; on the two anterior, somewhat rhomboidal 

 plates in the lower row these form a kind of oblique cross; on the third plate the 

 posterior arm of the cross bends upwards and continues as a medial ridge on the 

 two remaining, smaller plates of the lower row. On the plates of the upper row 

 the ridges form a kind of oblique T, the upper arm of the cross being absent. 



The first plate in the lower row covers at its anterior corner the upper part 

 of the supraclavicle and the hindmost corner of the skull and is closely attached 

 by means of dense connective tissue to the underlying bone, (supraclavicle I or) 

 posttemporal (pt); the lower margin of the same plate overlaps the upper part of 

 the clavicle. 



