384 
U. S. P. R. R. EXP. AND SURVEYS—ZOOLOGY—GENERAL REPORT. 
of a lighter, rather more yellowish tint. The caudal region is dark above and below. The fins 
are likewise dark. 
List of specimens. 
Catal. 
No. of 
Locality. 
Whence obtained. 
When 
Original 
Nature of 
Collected by— 
No. 
spec. 
collected. 
Number. 
specimen. 
981 
i 
Fort Steilacoom, Puget’s Sound.. 
Dr. Geo. Suckley... 
1855 
37 
Alcoholic. 
Dr. Geo. Suckley. 
SCOLECOSOMA, Girard. 
Gen. Char. —All the characters of Jlmmocoetes except the presence of one single dorsal fin instead of two, continuous with 
the upper lobe of the caudal. The anal is likewise rudimentary, else reduced to a mere ridge extending from the vent to the 
inferior lobe of the caudal. 
Three species, so far known, compose this genus: Ammocoetes concolor, Kirtl., from the 
hydrographic basin of the Ohio river; Ammocoetes unicolor, DeKay, from the fresh waters of 
the northeastern States; and Ammocoetes borealis, Agass., from Lake Superior. No repre¬ 
sentatives of it have, as yet, been observed west of the Mississippi valley. 
