580 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 4». 



An osseous crest not much unlike this is present in Car'jnodes and 

 Ictiohus, the elements being especially distinct in the latter (fig. 5). 

 It is rather feebly represented in Catostomus, where the coosified 

 part of the crest involves the spines and interneurals anterior to and 

 including the sixth vertebra. The fourtli, fifth, and sixth spines 

 only are easily distinguished, their tips extending upward astride a 

 knife-like blade formed by the ankylosed interneuriils. 



The skull of Xyrauchen differs greatly from that of Catostomus, 

 as will be seen by a comparison of the illustrations (figs. 3 and 4). 

 The fontanelle in Xyrauchen is broad anteriorly, narrow posteriorly, 

 almost triangular in shape, the posterior part continued baclvward 

 and upward as a narrow trough on the base of the occipital crest. 

 In Catostomus (insignis, commersoni, macrocJieilus, mniotiltus, ta- 

 Jioensis) the foramen is broad, oblong, and more or less rectangular. 



This and other peculiar cranial chai'acteristics of Xyrauchen indi- 

 cate no very close relationship between it and Catostomus. 



The doi-sal crest of the species is exaggerated in old age by the 

 flattening of the head, the doi-sal contour of which becomes strongly 

 concave in contrast to the convex skuUs of Catostomus, Caryiodes, 

 and others. 



Doctor Mearns notes that the flesh of this species is excellent and 

 of fine flavor. 



Specimens were collected in the Colorado at Yuma, where one 

 example with a peculiar abnormal squamation appeared, the scales 

 being only about half the usual size, except in several very restricted 

 areas, where a few normal ones were found. 



Very large specimens, refusing to take a hook, were snared in deep holes among 

 tlie rocks. A line with several hooks attached was allowed to sink to the bottom 

 and when a school moved over it the line was brought out with a sharp swish of the 

 pole, a sucker usually being hooked. 



The entire venti-al sm-face is orange yellow; pectoral and ventral fins very slightly 

 dusky, their upper surface marked basally with dusky olive; iris yellow, with 

 greenish-yellow granulation; lower third of head, including end of snout, orange 

 yellow, in strong contrast with the flesh-colored mouth; sides salmon color, granu- 

 lated with dusky olive; dorsal surface, including top of head, dark olive brown; 

 anterior ridge oii hump pale olive. Dorsal I'm olivaceous; anal orange yellow, indis- 

 tinctly marked with dusky; caudal yellowish olive. In some examples the fms are 

 rather rosy, and the scales of the sides are tipped with silvery. An occasional example 

 has the dorsal siu-face dark olive brown, and there is a strong pinkish tint below the 

 lateral line. 



Colorado River at Yuma; Gila River at Gila City. 



GILA ELEGANS Baird and Girard. 



There is one example in the collection which measures 15f inches 

 in length. The head is greatly flattened and a broad, rounded, 

 nuchal hump is developed. 



The very narrow caudal peduncle, the depressed and elongate 

 head, and the dorsal hump of 6^. elegans caUs to mind the fact that 



