544 PROP. T. W. BEIDaE Om THE MESIAL 



the others, are partially confluent proximallyand distally, although 

 separated centrally by large oval or elongated vacuities. The 

 fin-supports of a specimen of this character are represented iu a 

 figure by Mivart (I. c. pi. Ixxix. fig. 8), which is perfectly accurate 

 so far as the ventral segments are concerned, although, curiously 

 enough, the dorsal segments of the radial elements are neither 

 represented ia the figure nor referred to in the text. 



TELEOSTEI. 

 Phtsostomi. 



osteoglossid^. 

 Osteoglossum formosum. 

 Dorsal fin. — In a skeleton of this species in the Mason College 

 Zoological Museum there are eighteen soft fin-rays and nineteen* 

 radial elements in the dorsal fin. The penultimate radial element 

 consists of a proximal and a distal segment, the latter supporting a 

 fin-ray ; the last has only a proximal segment, and is also without 

 a fin-ray. All the remaining elements (PI. XXI. fig. 7), iucluding 

 the first, are trisegmental, and each consists of a long and some- 

 what dagger-shaped slender proximal segment (p.s.) ; a much 

 shorter, slender, and slightly hour-glass-shaped mesial segment 

 {m.s.) ; and a rounded, nodular distal segment (d.s.). All the 

 segments are completely ossified. The proximal segments exhibit 

 no trace of the strong lateral longitudinal ridges which in most 

 Teleosts separate the erector and depressor muscles of the fin- 

 rays while providing surfaces for their origin. The articular 

 interconnexions of the various radial elements for mutual support 

 are very similar to those of Amia and Lepidosteus. The slightly 

 enlarged distal extremity of each proximal segment is divided 

 into an anterior and a posterior facet. The posterior facet 

 articulates with the mesial segment, which is directed obliquely 

 backwards and upwards, and in turn articulates with the distal 

 segment, but the latter is also supported by the anterior facet of 

 the proximal segment of the next succeeding radial element. 



With the exception of the last, all the radial elements support 

 fin-rays. The cleft proximal end of each ray {f.r.) embraces the 

 distal segment of its proper supporting radial element, but 

 from what has been said as to the articular relations of each 



* Exclusive of a slender splint-like bone wtiicli is situated immediately 

 anterior to the first of the fin-bearing series, and is apparently a vestigial radial 

 element. > 



