EXPLANATION OF THE PLATES. 



Plates I, III, IV, and V are from photographs of fresh or preserved 

 specimens. The specimens in most cases were immersed in water or 

 alcohol, and photographed with a vertical camera. Plates VI, VII, and 

 VIII were drawn by Mrs. Gage from photographs or from the object by 

 the aid of a camera Incida. 



PLATE I. FIG. 1-2. 



A pair of lake lampreys abont 33 centimeters long, from the same 

 nest; obtained June 9, 1893. At the head of the article. 



Fig. I. Male lake lamprey showing dorsal ridge and the approxima- 

 tion of the two dorsal fins. This specimen weighed loi grams. 



Fig. 2. Female lake lamprey. The dorsal fins are not connected, and 

 no dorsal ridge is present, but the anal notch is marked. This female 

 had almost completed spawning, and hence appears slender. Compare 

 with the sea lamprey full of eggs (Fig. 17, PI. V). 



The stone to which the specimen is attached weighed 199 grams, the 

 specimen only 72 grams. While this pair were in the nest and under 

 observation the female was seen to drag this stone down the stream for 

 a considerable distance. 



PLATE II. FIG. 3-4. 



Map of the head of Cayuga Lake, showing the surrounding country 

 and the streams flowing into the lake. (From W. R. Dudley's Cayuga 

 Flora. ) The squares on the map are kilometers and the zero point is 

 the University Signal Station (U. S. S.) point of reference, a point on 

 the University campus, whose latitude and longitude have been deter- 

 mined with great accuracy by the Department of Civil Engineering. 

 Fig. 4, in the upper right hand corner, is a topographical map of the 

 lake basin designed especially to show the lakes and their outlet through 

 the Oswego River, the water-shed around the basin is indicated by in- 

 terrupted Imes, and also the water courses draining the elevation sur- 

 rounding the lake basin. It is to be noted that the Susquehanna River 

 with its tributaries is the most important of these. 



There is an important ridge between Lake Ontario and the interior 

 lake basin, and this elevation is drained by numerous small streams 

 flowing northward into Lake Ontario. It is to be especially noticed 

 also that this elevation is broken through by the Oswego River. 



L. Lake ; R. River ; Cnd. Canandaigua Lake ; Crkd. Crooked or 

 Keuka Lake ; Owsc. Owasco Lake ; Sktls. Skaneateles Lake ; Ond. 

 Onondaga Lake. Several small lakes have been omitted. , 



PLATE III. FIG. 5-10. 



Figures to represent the relations of the two dorsal fins in the male 

 lake lamprey in and out of the spawning season, the female in the 

 spawning season, and two larvae of very different sizes. 



