17 283 



sponding to the posterior one on the following vertebræ. From the anterior corner 

 of the expanded transverse process of the second vertebra (at * in PI. I, fig. 11) a 

 strong ligament passes to the posttemporal. The following free abdominal vertebræ 

 — lilie those of Aulostoma — are provided willi two transverse processes on each 

 side, but here the posterior process is always small compared with the anterior 

 (PI. II, fig. 9). The latter is especially large and distally flat and expanded on the 

 5—6 vertebræ immediately following the coalesced part. On the first caudal the 

 posterior process suddenly disappears. 



The inferior arch and spine form part of the anterior transverse process, 

 being formed by a process on each side from the base of its lower face. The 

 anterior 9 — 10 caudal vertebræ, which support the dorsal and anal fins, retain the 

 transverse processes and are, except the first, provided besides with an upper set 

 of similar, l)ut shorter and more slender, pointed lateral processes, originating from 

 the base of the neural arches. Behind these fins no lateral or transverse pro- 

 cesses occur. 



On all the free vertebræ articular processes are present, the anterior ones, as 

 in Aulostoma, being large and high; on the caudals behind the fins similar inferior 

 articular processes are developed. The vertebræ of the slender posterior part of 

 the tail have their upper and lower spinous processes depressed, lying flat and 

 overlapping caudally; at the end of the tail they rise again, and the last vertebra 

 takes on the shape of a vertical plate, probably representing two hypui-al bones. 



Ribs are wanting. 



Connected with the vertebral column are some osseous structures, the anterior 

 of which — the nuchal plates — are probably to be regarded as modified inter- 

 neural bones, while the others seem to be ossified tendons or ligaments. 



The three nuchal bones are longitudinal plates (firmly) joined together 

 and over-lapping each other towards the tail; Ihey are through connective tissue 

 fastened along the vertical lamella representing the modified spinous processes of 

 the first four elongated vertebræ. 



Their upper face is sculptured and more or less visible through the skin; 

 the lower face is concave and carries on the foremost part of the first plate a 

 short median keel, fitting into a much broader triangular excavation of the neural 

 spine of the first vertebra; on the hind part of the second plate a median furrow 

 begins and gradually deepens on the third into a narrow groove between two low 

 lamellæ, which are continued into long and thin prolongations, reaching backwards 

 along the spinous processes of the 9 or 10 anterior free vertebræ. 



The three nuchal plates are evidently homologous to the plates in the corre- 

 sponding position in Aulostoma; and as in the latter genus they are doubtless to 

 be regarded as modified interneurals, the same interpretation of the nuchal plates 

 in Fistularia seems justified. Small specific ditTerences are to be met with in the 

 nuchal plates: in Fist, petimba they are broader than in F. tahacaria; in the latter 

 the ventral median keel of the first plate (the rudiment of the "stem" of an ordinary 



D. K. D. Vidensk. Selsk.Skr., 7. Række, naturvidensk. og mathem. Afd. VIII. 5. 37 



