﻿46 



the fish 

 muscles. 



this line's continuation lies between the upper and lower lateral 



This line on the lateral plates is due to a very prominent, 

 thin ridge or lamella on their inner surface, which is joined to 

 the likewise lamellar-like transverse processes on the correspon- 

 ding part of the spinal column; an immovable connection is thus 

 formed between the exo- and endoskeleton. 



Examined more closely the condition is as follows (cf. fig. 1). 

 A little behind the anterior end of the lateral plate I arises a single 

 fold or ridge which soon divides into two lamellæ, an upper and 

 a lower, separated by a very narrow cleft; in this is set the ante- 

 rior end of the transverse process on the 2nd abdominal vertebra; 

 the two lamellæ fuse again to one, which, traversed by the suture 

 between plates I and II, is continued on plate II; between the two 

 plates the lamella has a deep notch; on the plate II, close behind 

 the notch, the lamella again becomes double and remains so nearly 

 to III, where it is single, then we have a notch, it becomes double 

 again on III and so on as far as IV. The thicker, middle part of 

 the transverse processes on the 2nd, 3rd and 4th vertebræ is inserted 

 in the notches, whilst the thinner, remaining part of the same 

 process is enclosed between the double lamellæ as in a sheath. 

 Each of the long transverse processes on the 2nd — 4th vertebræ 

 is thus inserted into two lateral plates; the transverse process on 

 the 5th vertebra on the other hand is only connected by its ante- 

 rior part with one plate, IV. On plate V the lamella is single and 

 low, and seems to be absent in A. scutata. 



Further constituents of the dorsal armour are, on each side, 

 the two plates scl and cl, PI. I, fig. 1, as also the dorsal spine T. 



The two former are in reality parts of the pectoral girdle; 

 the upper, scl, is the supraclavicular. It is connected anteriorly by 

 an articulation with the posttemporal (suprascapular, supraclavicula 

 I), pt, which forms part of the skull ; its other connections are 

 immovable; it meets above with dorsal plate I in a simple straight 

 suture, below with cl in a somewhat curved suture, posteriorly 

 with the anterior end of the lateral plate II in a dentated, oblique 

 suture. The lower plate cl is a good deal larger, elongated, some- 

 what crescent-shaped in A. scutata, shorter and relatively somewhat 

 higher in the other two species; the posterior point reaches the 

 upper edge of the base of the pectoral fin; the ventral border is 

 in contact for a long distance with the upper margin of the 5th ventral scutum in 

 scutata but not in the other species; the anterior part of the ventral border is in 

 contact with the small scutum S in all three species, over a fairly long distance 



1-6: 



Fig. 1. 

 Amph. scutata 

 first to sixth îil)dom 

 nul vertebræ seen 

 from below ; the exo- 

 skeleton has been re- 

 moved from the left 

 side: the hitcrnl plates 

 I~V are seen on the 

 right side: n : incision 

 in the transverse pro- 

 cesses for nerves ; cl : 

 upper margin of cla- 

 vicle. The numbers 

 /-/V point to theridge. 



