578 PROCEEDiyOS of the XATIONAL museum. vol.49. 



a member of the genus Pantosteus. The cotypes of jan'ovii can not 

 be fomid. Cope remarks that this is a less elongate species than 

 platyrhynchus, thus lending color to the supposition that his observa- 

 tions were made on an example of generosus. It is also worth while 

 to note that the original description refers only to " several specimens 

 from near Provo. Messrs. Yarrow and Henshaw." There can then 

 be no mistake as to the type-locahty, and apparently no good reason 

 to assume that any cotypes came from the Rio Grande.^ 



The Lahontan system has one species, P. lahontan Rutter,^ which 

 is related to P. platyrJiynclius, each resembling the other closely both 

 in cranial structure and external characteristics. One form, P. 

 jordani ^ Evermann described from the upper part of the Missouri 

 Basin, seems to be a representative of P. platyrhynchus, although the 

 fontanelle is reduced to a very narrow slip. But one species seems 

 to be known from the Rio Grande, Oatostomus plebeius Baird and 

 Girard.* It has the thick skull without fontaneUe characteristic of 

 Notolepidomy2on. Santa Ana River, a coastal stream of southern 

 California, contains one species santa-anae, a member of the same 

 genus. Its describer was mistaken in its relationships, having com- 

 pared it with wrongly identified specimens.^ 



The relationships here indicated, and which are beUeved to be in 

 harmony with both the structure and geographic distribution of the 

 species in question, may be indicated as foUows: 



Lips with a horny cutting edge; cranium thin; a narrow and usu- 

 ally sUtlike fontaneUe present (fig. 2): 

 Pantosteus — 



delphinus Colorado. 

 platyrhynchus Bonneville. 

 jordani Columbia. 

 lahontan Lahontan. 



Lips with a horny cutting edge; craniimi thick; no fontanelle 



(fig. 1): 



Notolepidomyzon — 

 clarki Colorado. 

 santa-anae Santa Ana. 

 generosus Bonneville. 

 plebeius Rio Grande. 

 The center of distribution of each genus is the Bonneville Basin. 



1 Bull. U. S. Fish. Conun., No. 12, 1S92, p. 56. List of specimens of PantosUus now found in the U. S. 

 National Museum. 



2 BuU. U. S. Fish Comm., Xo. 22, 1902, p. 1-16. 



' Bull. U. S. Fish Comm., Xo. 12, 1892, p. 51. The writer follows Jordan and Evermann in identifying 

 P. colujnbianus Eigenmann (Amer. Xaturalist, February 4, 1893, p. 151) with P. jordani, not having suffi- 

 cient material for a careful comparison. A few poorly preser\-ed specimens from the Columbia indicate 

 that this identification should be accepted provisionally, for the two may be distinct species. There is 

 danger of confusing this form with C. calostomus. The latter has a narrow, rectangular fontanelle. 



« Proc. Acad. Nat. Sci. Phila., 1854. p. 28. 



» Proc. U. S. Nat. ilus., vol. 34, 1908, p. 33. 



