THE ORDERS OF TELEOSTOMOUS FISHES 465 



forms ; tail hemiheterocercal (to homocercal) . Scales rhombic 

 or rhomboidal, generally arranged in oblique series, frequently 

 united above and below by peg-and-socket articulations, and 

 grading into very thin rounded or cycloidal scales, which greatly 

 overlap. The mandible retains splenial and coronoid elements. 

 The principal divisions of the superorder Lepidosteoidei may 

 be broadly sketched as follows: 



Suborder i. Mesoganoidei nom. nov. 



i. Trunk more or less fusiform. Mouth small, teeth either 

 styliform (Stylinodontidae, Macrosemiidae) , conical (Pholido- 

 phoridse) , or tritoral (Lepidotidae) . 



Stylinodontidas, examples: Acentrophorus, Trias, Up. Perm.; Semi- 



onotus (Ischypterus) Upper Permian to Upper Jurassic. 

 Lepidotidse, examples: Colobodus, Lepidotus, Trias to Cretaceous. 



2. Trunk more elongate, mouth larger, marginal teeth styli- 

 form. 



Macrosemiidas, examples: Macrosemius, Ophiopsis, Notagogus, Trias 

 to Cretaceous. 



3. Retaining rhombic ganoid scales, but approximating 

 in other characters toward the more generalized Isospondyles. 



Pholidophoridas, examples: Pholidophorus, Phioldopleurus, Trias-Jura. 

 Dapediidas, examples : Dapedius (placed near the Pholidophoridae by 

 Boulenger). 



Suborder 2. Pycnodonti Hay ex Agassiz 



Trunk deeply fusiform or cycloidal. Teeth, prehensile on 

 premaxillary and dentary, tritoral on vomer and splenial, form- 

 ing a highly specialized crushing apparatus. Systematic posi- 

 tion uncertain but apparently an offshoot of the Lepidotus -like 

 genera (Woodward, '98, p. 101). 



Pycnodontidse, examples: Pycnodus, Gyrodus, Microdon, Anomcedus, 



Lower Jurassic to Lower Eocene. 



Suborder 3. Aspidorhynchi nom. nov. 



(Aetheospondyli Woodward in part.) 



Swordfish-like Lepidosteoids, ordinally united by Woodward 



with the Lepidosteidae, but differing from them in the possession 



of a predentary or premandibular bone and in the more normal 



character of the vertebrae. 



