bra is also much smaller than in L. comuta and only con- 

 tacts the basal half of the rodlike portion of the last 

 pterygiophore. 



The last dorsal fin basal pterygiophore in the two 

 species of Tetrosomus is similar to that of L. fornasinii, 

 but the neural spines of the vertebrae below it are even 

 more reduced in size. In Tetrosomus the distal end of the 

 pterygiophore is only slightly expanded laterally and 

 posteriorly and the basal portion is rodlike, its extreme 

 basal end being supported variously by the long neural 

 spine of the Uth vertebra. The rest of the length of the 

 pterygiophore is not in contact with any other vertebrae, 

 mainly because the posterior extension of the distal end 

 is short and the neural spines of the 13th and 14th verte- 

 brae are extremely low. As in L. fornasinii, the trifid 

 neural spines of the 15th and 16th vertebrae in 

 Tetrosomus are not massive. 



The degree of development of lateral flanges extend- 

 ing down from the neural spines across the lateral sur- 

 faces of the centra to end in broad transverse processes 

 extending out anterolaterally from the lower surface of 

 the centra is difficult to compare between species other 

 than relatively subjectively. The flanges are best 

 developed in Lactoria and Ostracion, moderately 

 developed in Tetrosomus and Rhynchostracion and only 

 slightly, if at all, less so in Rhinesomus, and poorly 

 developed in Lactophrys and, especially, Acantho- 



stracion. Thus, there is a tendency for the Indo-Pacific 

 species to have the lateral flanges better developed than 

 in at least most of the Atlantic species. 



Probably associated with the more bulbous snout of 

 Rhynchostracion is the fact that the ethmoid in this ge- 

 nus is wider and more massive than in all other genera. 



Variation in the branchial arches of ostraciids is main- 

 ly confined to the presence or absence of minute and per- 

 haps nearly functionless teeth on the third pharyngo- 

 branchial. The second pharyngobranchial in all species 

 bears equally minute or only slightly larger teeth than 

 those of the third pharyngobranchial. The first pharyn- 

 gobranchial is a toothless suspensory element that is 



Figure 176.— Rhynchostracion 

 rhinorhynchus: ventral (left) and dorsal 

 (right) views of skull, 88.2 mm SL, Java. 



