i62 Natural History Bulletin. 



ent from the waters of Iowa. With the above explanations of 

 these few characters we will begin the list of species, adding 

 explanations of other characters as occasion may require. 



A Skull imperfectly developed. Mouth sub-circular, and without true 



jaws. (The Lampreys). \ 



Family i. PETROMYZONTID2E.— The Lampreys. 



Nostrils single on top of the head. Gill openings, 7 on each side of the head. 

 Skeleton cartilaginous. The mouth fringed and adapted for sucking. Body 

 eel-shaped and with no paired fins. Parasites on larger fishes. 



a Maxillary (supra-oral) tooth forming a crescent-shaped plate with a cusp at 

 either end, and sometimes with a median cusp. Discal teeth few. 



Genus i. Ammoccetes. — Dumeril. 



1. Ammoccetes branchialis. — L. — Brook Lamprey. 



In the spring animals of this species ascend small streams for 

 the purpose of spawning. They build their nests on the gravelly 

 bottom of clear, swift streams by excavating cavities in the 

 gravel from two to three inches in depth, and with a diameter 

 of from i^ to 2 times the length of the animal. The eggs 

 are deposited in the bottom of these nests and left to hatch. 



The time of spawning in this locality is from about April 

 15th to April 20th, (1889). If the Lamprey be taken at other 

 times of the year it is only when attached to some unlucky 

 fish. This species seldom exceeds a length of 6^ inches, 

 and is of no economic importance. Found in Europe and 

 known, at present, in this country only from Ithaca, N. Y., 

 central and southern Indiana, southern Wisconsin and Cedar 

 Rapids, Iowa. 



aa Maxillary tooth composed of two or three cusps placed close together. 

 Discal teeth numerous and in concentric series. 



Gemis 2. Petromyzon [Artedi). — L. 



2. Petromyzon concolor. — Kirtland. — Silvery Lamprey. 



Petromyzon castatteiis, Jordan, Man. Vert., 1887. 



The habits of this species are similar to those of the pre- 



