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nanifly the small plate s in PI. I, fig. 3, seems from its whole position between the 

 clavicle and the other plates in the ventral armour to correspond with the small 

 plate indicated bj' the same sign in Aniphisile (s in PI. I, fig. 1), but in the case of 

 the other plates I am unable to carry out a detailed comparison. Starling from 

 the position, however, that the more primitive features are to be found in Cen- 

 triscus. I should imagine that the condition in Amphisile has arisen in one of three 

 ways, as already indicated earlier (p. 50 (12)). The characteristic rachis on the 

 ventral plates of Amphisile together with the faint indications of ridges connected 

 with their lower ends, can also without difficulty be considered as having arisen 

 from the ridges on the plates in Centriscus^. 



(2). The true scales in Centrisciis have been described by L. Agassiz (la), 

 Kner (21b), Vaillant (33) and more especially by O. Hertwig (16). They consist 

 typically of a bony plate ("Basalplatte" Hertwig) imbedded in the cutis, from which 

 there issues a short, median stalk or keel, which again broadens out into the scaly 

 plate ("blattartige Knochenlammelle", Hrtw.), which is seen through the epidermis 

 as the true scale; this is provided on its upper surface with at least one median 

 keel, or with a smaller or larger number parallel to the first, all according to the 

 size of the scale; the posterior margin is more or less toothed. The basal plate is 

 typically rhomboidal, with angles drawn out into longer or shorter points; in many 

 cases however the regular type is changed, as the number of the points may be 

 increased or one or two may even disappear. The scale plate also varies a good 

 deal. The simplest scales are the small ones found on the eye and at the base of 

 the pectoral fins or the unpaired fins; some of these small scales have preserved 

 the original form as found in the young (see below), others present almost all 

 possible transitions to the complicated scale which Hertwig figures (16, PI. I, figs. 

 15, 16). The largest scales of the type represented in the figure cited are found 

 on the sides of the trunk. Immediately above the ventral plates the larger scales 

 are oblong, with basal plates which are likewise oblong but with the margins 

 between the anterior and posterior angles provided with more or fewer teeth. Still 

 longer and narrower scales, but of a fairly regular, rhomboidal shape and with 

 quite regular rhomboidal, basal plate are found above and in front of the eyes; 

 those on the snout are even longer, almost linear in form, with likewise linear 

 basal plates more than 3 mm. long. 



We find the original form of the scale in the young fishes. The Copen- 

 hagen Museum possesses a number of the developmental stages of Centrisciis, which 

 have been described and partly figured by Lütken (24 b); most of them are referred 

 by him to C. gracilis, which differs but little, in the dermal structures not at all, 

 from scolopax; some also belong to this species. In the youngest specimens, ca. 

 7 — 9 mm. (cf. Lütken (24 b), PI. I, fig. 6), both the scales and the armour are very 

 distinct. All the scales show the same form ; they consist of the future basal plate, 

 which is rhomboid with the angles drawn out into fine points; on their antero- 

 posterior diagonal there is a thin, vertical keel or comb which terminates poste- 



