28 Mr. C. T. Regan on the ' 



united with frontals ; subtemporal fossae very deep; no 

 Temporal depressions, but supra-temporal fosste more or less 

 distinct, open behind, roofed by the post-temporal and some- 

 times by tiie pterotic and parietal. Cleithra normally sus- 

 pended from supra-cleithra. Air-bladder divided into two 

 parts by a constriction, typically large and free, but sometimes 

 reduced {Discognatkus, Gyrinochilas), or the anterior part 

 sometimes enclosed in a bony capsule formed by the ossa 

 suspensoria {RliinQgohio, Saurogohio). Outer ramus of os 

 suspensorium not connected with its fellow nor with the 

 transverse process of second vertebra. 



A fontanel is usually absent, but in Saurogohio it extends 

 from the supra-occipital to the ethmoid, except for the frontal 

 bridge. The capsule enclosing the anterior part of the air- 

 bladder in Rhinogobio is quite remote from the transverse 

 processes o£ the second vertebra and is widely open behind. 

 In Saurogohio the posterior aperture is reduced and there 

 are lateral expansions with terminal orifices which bear some 

 resemblance to those of the Cobitidse; in this case, however, 

 the transveise processes of the second vertebra are free 

 except near their base, where they support the lateral ex- 

 pansions, and the cavities of the latter do not communicate, 

 with that of the capsule and apparently contain diverticula of 

 the paravertebral sacs. 



There are probably at least 1000 species known from North 

 America, Eurasia, and Afiica. 



A satistactoiy classitication of the genera cannot be arrived 

 at without monograpiiing the family, but the tullowing 

 remarks may not be out ot place. 



The greatest variety of genera and species is found in Asia, 

 which may be regarded as the original home of the group ; 

 and of all the genera which I have examined Opsariichthys 

 seems to be the most primitive. The terminal mouth, wide 

 gill-o|)enings, large pseuJobranchia?, median dorsal fin, 

 rounded abdomen, triserial pharj'ngeal teeth, complete series 

 of circumorbitals, large posterior temporal fossae, and separate 

 second and third vertebise are all features of generalization. 

 The foramen between quadrate and metapterygoid, so charac- 

 teristic of the Characiformes, is well developed in Opsari- 

 ichthys'^ this foramen is also present in Chela, but is absent 

 in all other Cyprinids. In Opsariichthys the cleithra are 

 formed much as in typical Characiformes, narrowing forwards 

 to a point; many other genera with strongly decurved 

 lateral line — Barilius, Danio, &c. — agree with Opsariichthys 

 in the form of the cleithra, rounded or pointed anteriorly, and 

 these are connected by genera such as Aspius with Leucucus 



