PANTOSTEUS JORDANI. 
53 
In all species of Catostomus examined ( C . latipinnis, catostomus, ardens, and gri- 
seus), the air bladder is large, very much larger than in any Pantosteus and very differ- 
ent in appearance except in G. latipinnis , in which the air bladder greatly resembles 
that of Pantosteus. 
Pantosteus jordani is rather intermediate in its structure between Pantosteus and 
' Catostomus , but, on the whole, its characters indicate a closer relationship with the 
species of the former genus, in which it should be placed if Pantosteus and Catosto- 
mus are to be regarded as generically distinct, the propriety of which is doubtful. 
The high development of the cartilaginous sheath is a character possessed by all the 
species of Pantosteus and is not found among the species of Catostomus, except in C. 
catostomus, where it is more pronounced than in any other species of that genus. 
The entire obliteration of the fontanelle, even in the most typical species of Pan- 
tosteus, is a question of age, the fontanelle being more or less evident as a very narrow 
slit in the young of all the species of which the young are known. 
Pantosteus jordani is, on the.one hand, most closely related to Pantosteus virescens 
Cope and P. discobolus (Oope), while on the other it resembles C. catostomus (Forst.)- 
It is the most abundant and most generally distributed species of the family in the 
streams flowing from the Black Hills, and frequents the clear, colder, and swifter 
parts of the streams. With the exception of Hat Creek, all the streams in which it 
has been found are clear and cold. We did not And it at all in the South Fork of the 
Cheyenne nor in the Loup or Beaver Creek at Ravenna. It is apparently a fish of 
small size which delights in the upper reaches and colder, clearer portions of the 
smaller mountain streams of the Upper Missouri basin. 
1 name this interesting, species for my teacher and friend, President David Starr 
Jordan, of Leland Stanford Junior University. 
Pantosteus jordani sp. nov. Jordan’s Sucker . About four-fifths natural size. 
In connection with my study of this species I was led to an examination of all the 
specimens of Pantosteus and the related species of Catostomus to be found among the 
collections now in the U. S. National Museum. Dr. Jordan, in his Catalogue of Fishes 
of North America, published in 1885, recognized but three species of Pantosteus, viz, 
'plebeius, generosus, and guzmaniensis, and expressed the opinion that Minomus bardus 
and M. delpliinus of Cope should be considered identical with P. plebeius, and further, 
that P. virescens Cope is the same as Acomus guzmaniensis Girard. 
