Lake Maxinkuckee, Physical and Biological Survey 307 



also has well-developed teeth and eyes before it reaches the size 

 of the specimens of /. aepyptera at hand. 



The following is a description of the specimen 116 mm. in 

 length : 



Head 5.8 in length; depth 19.3; dorsal finfold beginning as a 

 low ridge a short distance behind last gill-opening, reaching its 

 greatest height (about 8 mm.) a little behind vent, no notch sepa- 

 rating it from caudal ; caudal fold quite low ; the dorsal and ventral 

 folds extending nearly to end of body; barely any membrane 

 beyond caudal tip of body ; ventral fold similar to dorsal, beginning 

 as a mere ridge a little behind the last gill-opening. Body ellip- 

 tical in cross-section, not much compressed, the thickness from 

 side to side being about five-sixths the depth; gill-openings 7 in 

 number, branchial space about 9 in body; nostril small, single, 

 median, consisting of a small pore somewhat lengthened along the 

 axis of the body, surrounded by 3 low flaps forming an equilateral 

 triangle with one apex at the anterior end ; upper lip a prominent 

 horseshoe-shaped projection, thick at the base, thinner at the edges, 

 curving somewhat downward along each side and ending in a 

 rounded lobe; lower lip a low open V-shaped ridge; buccal disk 

 covered with small, somewhat fringed flaps or papilla?; teeth and 

 eyes not developed. 



Color: Back and sides slaty blue, belly whitish, the branchial 

 area somewhat paler than the remaining portion of the sides; the 

 small dusky spots mentioned in current descriptions as being pres- 

 ent above each gill-opening and usually conspicuous even in the 

 Iarva3, are not present in our (alcoholic) specimens. The num- 

 ber of muscular impressions between the last gill-opening and 

 vent in the specimens examined is somewhat larger than given in 

 current descriptions, there being 53 to 55 instead of 51. 



These larval lampreys are exceedingly active little creatures, 

 and move rapidly through the water or mud by quick lateral 

 flexions of the body, their actions much resembling those of some 

 of the aquatic salamanders in this respect. They appear to spend 

 most of their time in the mud, upon which they feed for the sake 

 of the microscopic organisms contained in it, and the fringed flaps 

 on the buccal area probably assist in washing the mud into the 

 mouth, or in selecting food. The stomach of an example 100 

 mm. long was examined. The intestine, a straight tube from the 

 mouth to the vent, was pretty well filled with mud. The mud was 

 examined and found to contain numerous diatoms, among 

 which Navicula was represented by several species; species of 

 Synedra, Epithemia, Gomphonema, Stauroneis and Cymbella and 



