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vertebiæ, and a posterior, including the remaining interspinals, beginning behind 

 the spinous process of the 6th vertebra; just as in Amphisile there are thus no 

 interspinous bones in front of the 5th and 6th vertebrae. 



In the first group the first two members have no fin-rays; the lower end of 

 their stem or main part (i. e. the part containing the cartilaginous axis) reaches 

 right down to the base of the spinous processes; at the tips of these the interspi- 

 nous bones broaden out into a thin vertical plate (= the "dagger-blade" of an 

 ordinary, typical interspinous bone); the upper margin of this is dilated trans- 

 versely and forms a kind of narrow roof along the middle line of the dorsum, 

 supplemented posteriorly by the corresponding part of the 3rd interspinous bone. 

 Seen from above this roof appears broadest in the centre; the central, longest and 

 broadest part belongs to the 2nd interspinous bone and is connected by means of 

 a forked suture at each end with the other two members; the roof, which is 

 directly under the skin, is covered with scales. The 3rd interspinous bone supports 

 a fin-ray, namely, the quite small dorsal spine (/?' in PI. I, fig. 3 and PI. II, fig. 2). 

 It is the longest and stoutest interspinous bone in the whole group; its thickened 

 stem, like the foregoing, is wedged in between two spinous processes, the 2nd and 

 3rd, reaching to their bases; at their upper end it likewise broadens out into a 

 thin, vertical plate; the hindmost part of this is somewhat thicker and has its 

 posterior margin rounded and fitted into a longitudinal furrow along the anterior 

 side of the 4th inters|)inal; the upper end of the hind margin forms a small 

 thickening, which terminates in a short, slightly hooked spine. Upwards the stem 

 becomes thicker and immediately under the skin forms a kind of longitudinal 

 protuberance (/), longitudinally grooved; the upper pointed end of the posterior 

 plate in the upper row of the dorsal armour is firmly connected with this. The 

 4th interspinous bone bears the enormous dorsal spine, the 2nd fin-ray (R), and 

 seems at first glance to be more like the common type of interspinous bone in 

 bony fishes; its lower end is wedged in between the spinous processes of the 3rd 

 and 4th vertebræ but does not go so far down as the previous. Closer examination 

 shows the same parts as on these; the stem is here very strong, especially at the 

 upper end ; the anterior blade is here represented by a low, longitudinal ridge, 

 with a deep furrow for the reception of the posterior edge of the 3rd interspinal; 

 the posterior blade is low and thin (it separates the two musculi depressores for 

 the large spine, just as the anterior blade along with the hindmost blade of no. 3 

 separates the M. erectores); it is only at its upper end that it becomes heavier and 

 forms there a considerable, compressed process (/ in fig. 2, PI. II), the point of 

 which is received into a deep furrow on the anterior face of the following, the 

 5th interspinal. On each side of the upper end of the broad and heavy stem 

 there is a small, independent piece, oval above, triangular below, / in fig. 2, PI. II. 

 In position this corresponds well with the thickening (/') on the 3rd interspinal, 

 with which the 3rd dorsal plate is connected; but here it (/) is connected by suture 

 with the interspinous bone; the sutures may often be very difficult to see, but by 



