PINS OP GANOIDS AND TELEOSTS. 5S1 



spines between which they are interposed. In addition to the 

 lateral longitudinal bony ridge, each segment is furnished with 

 two lateral bony processes projecting outwards at right angles 

 to its long axis from a point a little below its distal end. The 

 distal segments are also similar to those of Balistes in their 

 relations and connexions infer se, the mobility of their articula- 

 tion with the proximal segments, and in their mode of insertion 

 into the cleft bases of their fin-rays. 



Anal Jin. — In almost every respect the anal fia is similar to 

 the posterior dorsal fin. 



GrTMNODONTES. 

 Tetrodon immaculatus. 



Dorsal fin. — In this species the single short dorsal fin, which 

 is apparently the equivalent of the posterior dorsal fin of the 

 preceding species, consists of ten soft rays supported by a series 

 of seven radial elements (PI. XXIII. fig. 35, r.e.^-r.e.''). All the 

 elements are bisegmental. Their proximal segments {p.s.) are 

 elongated and somewhat irregular in shape, without any trace of 

 the usual lateral longitudinal ridges, and all are more or less 

 firmly connected together for a portion of their length by 

 squamous sutures. The cartilaginous distal extremities of the 

 segments fuse together into a continuous peripheral margin 

 {cm.), which is separated from, but at the same time loosely 

 connected with, the distal segments by an intervening tract of 

 fibrous tissue (J.g-). 



The distal segments are represented by a series of simple, 

 cubical, cartilaginous nodules {d.s.), widely separated from t:ie 

 proximal segments, although corresponding with them in 

 number. As in the two preceding species, the distal segments 

 are intimately connected together in a longitudinal series by 

 fibrous tissue. 



The ten fin-rays have cleft bases, into which are inserted the 

 supporting distal radial segments. Towards the hinder part of 

 the fin more than one ray may be wholly or in part supported 

 by the same distal segment. 



Anal fin. — In this fin there are only four radial elements 

 (fig. 36, r.e.^-r.e.*), but at least ten soft fin-rays. The proximal 

 radial segments {p.s.) are firmly connected together although, 

 perhaps, less intimately than in the dorsal fin, and the first of 



