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Show 296 MR. C. TATE REGAN ON [Nov. 4, Family 2. D io d o n th x e . All the praecaudal vertebrae with bifid neural spine; anterior caudals with bifid divergent haemal spines instead of closed haemal 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 well-developed. Interoperculum rod-like, attached posteriorly to the rod-like anterior limb of the suboperculum. In other characters essentially similar to the Tetrodontidae, 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 : D iod o n , corresponding to Diodon, Chilomycterus, Dicotylichthys, and Atopomycterus of Gunther's Catalogue, of which Trichodiodon and Trichocyclus are probably young forms; and L yosph^e r a . 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 nostrils, 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. D iodon 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. L yospHjERA Evermann & Kendall.-Body oblong ovoid, coveied with feeble spines attached to papery plates. Caudal peduncle very short. Two nostrils in a tubular papilla. D. 11. A 4. Family 3. M olid^e . Praecaudal vertebrae without parapophyses ; anterior praecaudals with divergent bifid neural spines and neural canal not roofed in ; no epipleurals. Praeorbital 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 toothless ; fourth upper 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; pseudobranchias present1 ; six brancliiostegals, the first not enlarged. Skin 1 The " accessory opercular g ill" of so many authors is only a well-developed pseudobranch. |