226 L. Agassiz on the Ichthyological Fauna of Western America, 
Fig. 15 and 16 rep- 
resent the pharyngeals 
and teeth of these two 
genera side by side: 
15, a, the right pha- 
ryngeal of Chrosomus 
erythrogaster, band c 
one tooth in profile and from the grinding surface. Fig. 16, a, the 
right pharyngeals of Phoxinus varius of Europe, b, c, d, a tooth 
of the outer row from three sides. 
In my paper upon some new species of Cyprinoids from the 
Lake of Neuchatel, printed in 1835 in the Transactions of the Nat- 
ural Historical Society of that city, I characterised the genus 
Phoxinus as follows: “Body cylindrical, stout, covered with 
very small scales. Pharyngeal teeth pointed. Caudal furcate.” 
Heckel in his Ichthyology of the Travels of Russegger, has addet 
the following particulars: Dentes raptatorii 2-5; 5-2. Os anti- 
cum ; labia teretia; cirri nulli. Pinna dorsalis et analis brevior, 
illa pone pinnas ventrales incipiens. Squame minime mem- 
branacez, adherentes, vix se invicem tegentes. 
The facilities 1 have had for comparing Phoxinus and Chroso- 
mus, which are representative genera, respectively limited to the 
Old and New World, enable me to furnish further information 
upon their peculiarities, which is the more needed as the descrip- 
tion of Rafinesque is very brief and incomplete. : 
The bluntuess of the head and the shortness of the cylindrical 
body of Phoxinus is very characteristic and contrasts in a striking 
manner with the more pointed head and fusiform body of Chro- 
somus. In both these genera the scales are very small, thin, 
membranaceous and hardly appressed to the body, which circum- 
stance has misled Heckel into the statement that the scales hardly 
cover one another; yet they are imbricated in the usual manner ; 
but they are not arranged in quite so regular rows as in most other 
genera. Phoxinus and Chrosomus are in fact with Moxostoma 
the only groups I know in the family of Cyprinoids in which the 
lateral line is not regularly continuous from the upper angle of 
the opercle to the base of the caudal. In Phoxinus it breaks Up 
for the most part, not far behind the tip of the pectorals, but re= 
appears generally above the ventrals for some short space, and 
here and there single perforated scales may be traced to the end 
of the tail; in Chrosomus it is more continuous, extending usu- 
ally without interruption as far back as the space between the 
ventrals and the anal, and then more interruptedly back wards. 
The scales themselves differ so far that they may be recognizee, 
even when isolated ; in Chrosomus the concentric ridges upo? 
the surface of the ornamented layer of the scale are closer to- 
gether and interrupted at regular intervals in every direction !F 
D 
