FISHES OF PENNSYLVANIA. 
Chass CYCLOSTOML. Tan Myzonts. 
ORDER HYPEROARTIA. 
Famity PETROMYZONTIDA. Tue Lanpreys. 
Genus AMMOCCETES Dumenrt.. 
The genus Ammocetes is best distinguished from Petromyzon by the 
structure of its so-called maxillary tooth, which has the form of a cres- 
cent-shaped plate with terminal cusps and sometimes an additional me- 
dian cusp. In Petromyzon this bony plate is short and contains two or 
three teeth, which are very closely placed. 
1. Ammoccetes niger Rarrnesque. 
The Brook Lamprey. (Figure 16.) 
The high dorsal fin is divided into two parts by a deep notch. Several of the teeth 
on the side of the buccal disk are bicuspid and the rest simple. The mandibulary 
plate is nearly straight and has eight or ten cusps of nearly equal size. The length 
of the head, including the gills, is contained four and three-fourths times in the total. 
There are sixty-seven muscular impressions from gills to vent. In the spring a 
prominent anal papilla is present. The head is longer than the space occupied by 
the gill-openings and is contained eight and one-third times in the total; the depth, 
fourteen times. The eyes are large. The mouth is moderately small. The lips are 
conspicuously fringed with papille. The teeth change considerably with age ; young 
examples have no median cusp on the maxillary pJate. This lamprey is bluish- 
black above, the lower parts silvery. 
The brook lamprey or mud lamprey, also known as the small black 
lamprey, 1s found in the Great Lake region, the Ohio valley and the 
upper Mississippi valley. It occurs also in Cayuga lake, New York. 
According to Jordan it ranges west to Minnesota and south to Kentucky. 
It grows to a length of eight inches. Dr. Jordan considers it identical 
with the common brook lamprey of Europe, A. branchialis. The brook 
lamprey ascends the small streams in the spring to spawn just as the 
silver lamprey does. It is parasitic, and its spawning habits are similar 
to those of the sea lamprey. It clings to stones and clogs of earth while 
depositing its eggs, and is believed by some persons to die after spawn- 
ing. The probability is that it goes into deep water, where it remains 
until the spawning season again approaches. 
