296 MR. C. TATE REGAN OX [NoV. 4, 



Family 2. Diodoxtid^. 



All the prsecaudal vertebrae with bifid neural spine ; anterior 

 caiidals with bifid divergent hsemal spines instead of closed 

 hfemal arch. Behind the dorsal and anal fins the neural and 

 haemal spines are single, but bifurcate distally. Teeth in the 

 jaws coalescent, forming a beak without median suture ; internal 

 dentigerous plates M^ell-developed. Interoperculum rod-like, 

 attached posteriorly to the rod-like anterior limb of the sub- 

 operculum. In other characters essentially similar to the 

 Tetrodontidse, but with a less strongly ossified skeleton and larger 

 dermal spines. 



I am inclined to think that only two genera are capable of 

 clear definition : Diodox, corresponding to Diodon, Ghilomycterus, 

 Dicotylichthys^ and Aiopomi/ctervs of Gunther's Catalogue, of 

 which Ti^ichodiodon and Trichocychts are probably young forms ; 

 and Lyosph^ra. 



The skeleton is in all exactly similar, and the differences in 

 the nasal organs are not well marked, as although some species 

 have a tubular papilla with two nostiils, others a two-lipped tube, 

 in many of the former the septum between the nostrils is so easily 

 and so often torn that the condition in the latter results. Also 

 those species with two-rooted movable spines are connected with 

 those with three-rooted fixed spines by a series of species with 

 both sorts of spines in varying proportions. 



Genera. 



1. Diodox Linn. — Body stout, with strong spines. Nostrils 

 in a tubular papilla, sometimes confluent. D. 10-15. A. 10-15. 

 Vertebrae 21 or 22. Frontals much expanded. Post-frontals in 

 contact with supraoccipital, separating parietals and frontals. 



2. LYOSPHiERA Evermann & Kendall.- — Body oblong ovoid, 

 covered with feeble spines attached to papery plates. Caudal 

 peduncle very short. Two nostrils in a tubular papilla. D. 11. 

 A. 4. 



Family 3. Molid^. 



Praecaudal vertebrae without parapophyses ; anterior praecaudals 

 with divergent bifid neural spines and neural canal not roofed in ; 

 no epipleiirals. Pr^orbital not ossified ; no distinct bony nasal 

 cavity ; palatine firmly united to the skull ; praemaxillaries not 

 protractile, firmly united to the maxillaries ; teeth in the jaws 

 coalescent, forming a beak without median suture ; palate tooth- 

 less ; fourth uppei' pharyngeals present, toothed ; lower pharyngeals 

 separate ; interoperculum rod-like, attached posteriorly to the 

 rod-like anterior limb of the suboperculum. Two nostrils on each 

 side. Gills four, a slit behind the fourth ; pseudobranchiae 

 present ^ ; six branchiostegals, the first not enlarged. Skin 



^ The " accessory opercular gill " of so many authors is only a well-developed 

 ])SCudoljraiicli. 



