378 
U. S. P. R. R EXP. AND SURVEYS-ZOOLOGY-GENERAL REPORT. 
List of specimens. 
Catal. 
No. 
No. of 
spec 
Locality. 
When collected. 
Whence obtained. 
Nature of 
specimens. 
Collected by— 
974 
i 
Ft. Reading', Cow co., Sacramento 
river, California. 
1856 
Dr. J. F. Hammond. 
Alcoholic .. 
Dr. Hammond. 
2. PETROMYZON CILIATUS, Ayres. 
Spec. Char. —Body sub-cylindrical, deeper than broad, caudal region very much compressed. Buccal disk sub-elliptical, 
fringed upon its periphery. Head constituting about the tenth of the total length. Anterior dorsal fin lower than the second, 
and separated from it by a space equal to the fifth of its length ; its origin being nearer the extremity of the snout than the tip 
of the caudal. Inferior lobe of caudal fin deeper than the upper. Color olivacecus brown, rather dark above and more 
greenish beneath. 
Syn. —Petromyzon ciliatus, Ayres, in Cal Acad. Nat. Sc. I, 1855, 44. 
Having before us a specimen twenty-four inches and a half in total length, labelled by Dr. 
Ayres himself, there is no room to doubt as to species which we record in this paragraph. 
The body anterior to the dorsal fin is sub-cylindrical, deeper than broad, whilst it is com¬ 
pressed posteriorly to it, becoming more and more so towards the caudal region, which is very 
much compressed and quite thin. 
The head is sub-conical, tapering anteriorly, and smaller than the chest. Measured from the 
extremity of the snout to the first branchial orifice it forms about the tenth of the total length. 
The buccal disk is of moderate development, sub-elliptical in shape, continuous all around ; its 
periphery being provided with a series of small tentacles or fringes, with filiform tips and 
somewhat flattened bases, inserted upon the black edge of the thickened lips. Immediately 
within these fringes may be observed a continuous circular series of very small acute teeth, 
from fifty-five to sixty in number, each surrounded by a little circular depression, with a raised 
margin. When removed these teeth leave behind them small nipple-like papillae as the base 
upon which they were inserted. Within these teeth or papillae, as the case may be, we observe 
larger teeth. Seven rather small acute and conical ones occupy the anterior portion of the 
buccal ellipsis, disposed upon two series—five belonging to the continuous series and two 
forming an additional series in front; four larger ones on either side, the two middle ones 
tricuspid, the upper and lower pair being bicuspid ; eighteen very small, simple, conical, acute 
teeth like the preceding row complete this series, standing in a circular depression like those 
above alluded to. The buccal orifice, properly so called, is provided anteriorly with a tridentate 
transverse piece, the middle tooth being considerably smaller than the lateral ones ; posteriorly 
or interiorly is another transverse piece armed with five teeth, the three middle ones being 
somewhat smaller than the exterior two. At the entrance of the esophagus we observe three 
elongated, finely serrated pieces, the uppermost two placed vertically, the inferior one hori¬ 
zontally. The eyes are sub-elliptical; the longitudinal diameter of the orbit entering about 
eight times in the length of the side of the head from the first branchial orifice forwards 
They are nearer the latter than the extremity of the snout. The seven branchial orifices are 
vertically sub-elliptical, extending over a space somewhat longer than the cephalic region. 
The structure of these orifices is quite complex ; they are surrounded interiorly by a smooth 
