O. TUBERCULATUS • O 



a LENTIGINOSUM ■ D 



A. OUADRICORNIS ▼ V 



A. POLYGONIUS • O 



I I 



8 9 10 11 12 13 



JUMBER OF TEETH 



another and to the basioccipital and exoccipital basally, 

 while distally there is only partial fusion of their neural 

 spines. The third and fourth vertebrae are similarly fully 

 fused with one another basally, while their neural spines 

 are only partially fused. The degree of fusion of the 

 neural spines increases with increased specimen size, 

 much as described by Tyler (1963a) (or Acanthostracion 

 quadricomis. But even in the two largest specimens of 0. 

 tuberculatus examined (96.7-122 mm) the fused first- 

 second vertebrae and the fused third-fourth vertebrae re- 

 main distinct from one another. In 0. lentiginosum the 

 two smallest specimens examined (24.4-33.2 mm) have 

 the first and second vertebrae fully fused to themselves 

 and to the basioccipital and exoccipital basally, with the 

 neural spines only partially fused, and the third and 

 fourth vertebrae are similarly fused to themselves, with 

 the second and third remaining separate. But in all of the 

 larger specimens (68.2-115 mm) the fused first-second 

 vertebrae and the fused third-fourth vertebrae are at 

 least partially fused together between the second and 

 third, and in the largest specimens almost completely 

 fused. However, this variously partial to almost com- 

 plete fusion between the two fusion complexes in 0. len- 

 tiginosum is less complete and occurs at a larger 

 specimen size than in the other Indo-Pacific genera. 



The divergence of the haemal canal away from the 

 midline under most of the unfused abdominal vertebrae 

 is highly variable. There follows a listing of the course of 

 the divergence in the specimens closely examined for 

 it: Tetrosomus concatenatus, to the right of the mid- 

 line in 1 specimen; T. gibbosus, left in 1; Lactoria cor- 

 nuta, right in 4, left in 1, alternately right and left in 2, 

 almost straight in 1; L. fornasinii, right in 1, essentially 

 straight in 2; Ostracion lentiginosum, right in 4, left in 1; 

 0. tuberculatus, right in 5; Rhynchostracion rhinorhyn- 

 chus, right in 1; Acanthostracion quadricornis, right in 6, 

 left in 2; A. polygonius, right in 1, alternately right and 

 left in 1; A. guineensis, alternately right and left in 1; A. 

 notacanthus, right in 1; Lactophrys trigonus, right in 2, 

 left in 1, alternately right and left in 2; Rhinesomus 

 bicaudalis, left in 2; R. triqueter, left in 2, alternately 

 right and left in 2, almost straight in 1. Thus, in both the 

 Indo-Pacific species and in the Atlantic species, the 

 canal can be diverted to either the right or left, or al- 

 ternately to the right and left. If enough specimens were 

 examined it might be possible to show that there was a 

 greater frequency of right deviation in the Indo-Pacific 

 species and of left or alternately right and left deviation 

 in the Atlantic species, but such cannot yet be done. 



The structure of the last few vertebrae shows interest- 

 ing variation, as described by Tyler (1970b) and briefly 



Figure 166.— Number of teeth in upper (solid 

 symbols) and lower (open symbols) jaws in relation 

 to standard length, to show the slightly greater 

 number of teeth in the upper versus the lower jaw, 

 and the relatively negligible increase in number 

 of teeth with increasing standard length at sizes 

 greater than about 40 mm SL: Ostracion 

 tuberculatus, O. lentiginosum, Acanthostracion 

 quadricornis, A. polygonius. 



229 



