be changed, a detailed osteological description of C. 

 rostrata is given here for the sake of comparison with that 

 of another, less specialized, tetraodontid, Lagocephalus 

 laevigatas. 



Following below is first a discussion of the differences 

 between Canthigaster and the other tetraodontids, and 

 then of the anatomical diversity of the Tetraodontinae. 



The species of Canthigaster are distinguished from one 

 another externally primarily by coloration, with slight 

 aid from the number of dorsal fin rays, one species (am- 

 boinensis) usually having 11 or 12 rather than 9 or 10, 

 and perhaps from the caudal peduncle length versus 

 depth (differences between species not yet well worked 

 out). The species are as similar internally as externally, 

 there being an unrelieved sameness in the osteological 

 configuration: 1) the vertebral column is always highly 

 arched; 2) the haemal arches of the first three vertebrae 

 are relatively well developed although they do not usual- 

 ly completely enclose the haemal canal (first arch some- 

 times complete); 3) the haemal spines of the other 

 abdominal vertebrae are well developed and have a char- 

 acteristic rounded and flattened posterior lobe; 4) the 

 haemal spines of the caudal vertebrae are also well 

 developed and of similar shape in all the species; 5) the 

 neural spines of the first three vertebrae are bifid and 

 that of the fourth is bifurcate anteriorly; 6) the neural 

 spine of the seventh abdominal vertebra is always a long 

 shaft lying along the anterior edge of the first basal 

 pterygiophore of the dorsal fin, while the neural spines of 

 the successive vertebrae until the antipenultimate are 

 also elongate shafts; 7) the neural spine of the 

 antipenultimate vertebra is slightly expanded antero- 

 posteriorly and that of the penultimate even more so; 8) 

 the caudal fin supporting skeleton is essentially similar 

 in all species; 9) the basal pterygiophores of the dorsal fin 

 are all placed between the neural spines of the seventh 

 abdominal to the third caudal vertebrae; 10) the basal 

 pterygiophores of the anal fin are supported mostly by 

 the haemal spines of the first to third caudal vertebrae 

 but sometimes with assistance of the fourth; 11) the first 

 basal pterygiophores of the dorsal and anal fins are 

 always much larger than the others; 12) the supraneural 

 is similarly well developed and usually arched; 13) the 

 snout is relatively long and narrow; 14) there is always 

 only one hypohyal; 15) there is never an interhyal; 16) 

 there is only a slight trace of the dorsal roof of the 

 myodome; 17) there are never trituration teeth; 18) the 

 parasphenoid never has a dorsal flange in the orbit to the 

 frontals; 19) the pharyngobranchial of the first arch 

 always bears small teeth; 20) the supraoccipital is always 

 high crested; 21) the ethmoid is extremely long and T- 

 shaped; 22) the frontal has a pair of posterolateral wings 

 meeting or closely approaching one another distally; 23) 

 the prefrontal is flattened dorsally and gently down- 

 curved anterolaterally and is always placed in about the 

 middle of the skull; 24) the sphenotics are not much ex- 

 posed on the dorsal surface of the skull; 25) the vomer is 

 always well developed and relatively well compressed 

 laterally and well removed from the prefrontals; and 26) 

 the parasphenoid always has a deep keel. 



