FISHES—PETROMYZONTIDAE —PETROMYZON TRIDENTATUS. 
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Syn. — Petromyzonidae, Bonap. Sugg. Distr. metod. Anim. Vertobr. 1831, 123.— Dekay, New Y. Faun. IV, 1842, 379.— 
Storer Synops. 1846, 265. 
Petromyzontidae, Owen, Lect. Comp. Anat. Vertebr. anim. 1846, 48.— Bd. Iconogr. Encycl. II, 1850, 206.— Agass. 
Lake Super. 1850, 249. 
Petromyzonini, Bonap. Sagg. Distr. metod, Anim. Vertebr. 1831, 123.— Mull, in Weigm. Archiv fur Naturg. 1845, 
I, 137. 
Two out of the four genera which at present compose this family ( Petromyzon and Ammoccetes ) 
have representatives on the western as well as eastern coast of North America. 
PETROMYZON, Linn. 
Gen. Char. —Buccal disk funnel-shaped, sub-terminal, inferior, sub-circular or sub-elliptical, sometimes ciliated or fringed 
upon its periphery. Two vertical, finely denticulated, jaw pieces, one on either side of the esophagus ; a similar piece placed 
horizontally below the former. Teeth within the buccal disk disposed upon concentrical series, largest inwardly, simple, 
bicuspid and tricuspid. Two distinct dorsal fins ; second one united to the caudal and the anal. Gills in separate partitions of 
file chest. 
Syn. — Petromyzon, Linn. Syst. Nat. ed. XII a 1766, 394.— Gmel. in Linn. Syst. Nat. ed. XIII a I, in, 1788, 1513.— Dum. 
Zool. analyt. 1806; in Mag. Encyl. 1808 ; & Ichthyol. analyt. 1856, 112.—Cuv. Regn. anim. II, 1817, 117 ; 
2d ed. 1829 ; & ed. illustr. Poiss. 380.— Storer, Rep. Fish. Mass. 1839, 195 ; &, Synops. 1846, 265.— 
DeKay, New Y. Faun. IV, 1842, 379. 
The genus Petrorjiyzon, as characterized above, is restricted within narrower limits than those 
assigned to it by all previous writers on this subject. Such as it is given here it will include 
P. marinus, Tj. •, P. fluviatilis, L.; P. americanus , Lesu. ; P. nigricans , Lesu. ; P. tridentatus, 
Gairdn.; P. ciliatus, Ayres; P. plumbeus, Ayres; P. niger* and P. borealis. f The first 
two on the list being European ; the rest belonging to North America. 
1. PETROMYZON TRIDENTATUS, Gairdn. 
Spec. Char. —Body anteriorly sub-cylindrical, deeper than broad; posteriorly compressed, especially the caudal region. 
Buccal disk sub-circular, longitudinal diameter somewhat greater than the transversal, not fringed upon its periphery. Head 
constituting about the tenth of the total length. Anterior dorsal fin much lower than the second and separated from it by 
a space equal to the third of its own length ; its origin being nearer the extremity of the snout than the tip of the caudal fin. 
Upper lobe of caudal somewhat deeper than the lower lobe. 
Syn. — Petromyzon tridentatus, Gairdn. in Lit. : Richards. Faun. Bor. Amer. Ill, 1836, 293.— De Kay,N. Y. Fauna, IV, 
1842, 382.— Storer, Synops 1846, 266. 
We refer to this species a specimen from eighteen to nineteen inches in total length, since 
it agrees better with the description given by Sir John Richardson than any of the others from 
western America with which we are, so far, acquainted; it being in such a very precarious state 
of preservation that we cannot enlarge upon the above diagnostic characters, which we offer as 
approximative until they can he verified upon specimens in a better state of keeping. The 
head is nearly as long as the chest. The branchial orifices are smaller than in the following 
two species, and their structure, as far as a superficial examination may determine, is different 
also. The “ circular row of small nipple-like papillae, about fifty-six in number, and standing 
in the middle of little circular depressions having a raised margin,” &c., are the base of 
insertion of very small and acute teeth. The “ transverse row of four teeth” consists of six in 
the specimen before us, the two middle ones being the largest of the series. 
The coloration is too far gone to allow any allusion in regard to it. 
* Petromyzon nigrum, Rafin. Ichthyol. Ohiens. 1820, 84. 
t Petromyzon Jluvialis, Richards. Faun. Bor. Amer. Ill, 1836, 294. 
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