SEA LAMPREY OF CAYUGA LAKE 



573 



Figure 7. — Comparison of body sections of sea lampreys from Cayuga Lake and Seneca Lake. Measurements are given 

 in thousandths of the total body length. (Description of symbols in caption of fig. 1.) 



Teeth and myomeres. — Methods outlined by 

 Hubbs and Trautman (1937) were followed in 

 counting teeth and myomeres. Many of the diffi- 

 culties they encountered in work on Icthyomyzon 

 were present also in work on Petromyzon. Most 

 troublesome was the myomere count on imma- 

 ture specimens, especially those that had been 

 preserved for several years. In such specimens, 

 the myomeres were nearly indistinguishable ex- 

 ternally. It was necessary to slit the abdomen 



498325 O— 59 2 



lengthwise, in the ventrolateral area, and count 

 the muscle bands. 



In addition to the myomeres the following series 

 of teeth or cusps were counted: Cusps on the 

 supraoral lamina; number of biscuspid circum- 

 orals; teeth in the anterior row; cusps on the 

 lateral lingual lamina; cusps on the transverse 

 lingual lamina; teeth in the lateral row; teeth in 

 the circumoral row; and cusps on the infraoral 

 lamina. 



