7 273 



Ribs are wanting. 



Inter spinous bones are developed not only in connection with tbe dorsal 

 and anal fin rays, but in front of the dorsal fin a row of 9 or 10 rayless inter- 

 neurals is found, beginning immediately behind the skull. The three foremost of 

 the latter (PI. II, fig- 10, 1—3) are more or less distinctly seen through the skin, 

 which is here naked as already mentioned above, but the following 6 or 7 are 

 hidden below the scales. They all consist of a horizontal part, lying below the 

 skin in the shape of a longitudinal shield or plate, and a vertical part; they corre- 

 spond in position to the anterior 9 — 10 vertebræ, their vertical part being really 

 interposed in front of the spinous processes of the latter. This fact is less evident 

 in the case of the four elongated and fused vertebræ, but very easily seen in the 

 following free vertebræ. The modified interspinous bones form a continuous row, 

 in which not only the horizontal shields are joined (through sutures) but also 

 the vertical parts. The anterior three* are much larger than the rest, which 

 decrease evenly in size backwards, especially with regard to their shield-parts. The 

 upper face of the latter is sculptured with quite regular longitudinal striæ on the 

 3 anterior ones; feeble traces are seen on the fourth and still some faint and in- 

 distinct remnants may be observed on the following one or two. From the hind 

 margin of the second passes out on each side a long, flat and slender splint of 

 bone, looking like an ossified tendon fused to the shield; similar, but much 

 shorter ones proceed from the posterior margin of the following shields, except the 

 last, and are concealed below the plate of the next shield, while the long "cornua" 

 from the second nuchal shield diverge among the muscles. 



The vertical part (the main part or stem of the typical interspinous bone) is 

 elongated longitudinally according as the upper edge is modified into a shield; it 

 is most elongated and at the same time lowest in the 3 foremost interneurals (the 

 "nuchal shields"), increasing in height backwards with decreasing length; its lower 

 margin is cleft, thus embracing the crest formed by the fused arches and spinous 

 processes. The foremost as well as the fourth to the tenth interneurals show most 

 distinctly that the position is originally in front of the corresponding spinous pro- 

 cesses as is usually the case in fishes The foremost is connected with the supra- 

 occipital by ligament. Immediately behind the row of rayless interneurals appear 

 those supporting the (9— )10 isolated rays, which together constitute the first dorsal 

 fin; each ray of the latter is a spine having a small separate fin-membrane. These 

 interneurals are considerably smaller than the preceding and of a different shape 

 (PI. II, fig. 10, 10 — 16); they do not form a closed row nor do they reach to their 

 corresponding vertebræ. The foremost corresponds to the 11th (or 10th) vertebra, 

 between each of the following is an interspace with one or two spinous processes. 



* Only these three "shields" have been mentioned previously. Güntheh (16a p. 537) says: 

 "A long narrow bony shield, half as long as the snout, is joined to the occiput and extends along the 

 neck." But I.e. p. .538 he sajs {A. chinenser. "the three single plates of which the nuchal shield is 

 composed are more distinct." 



