FISHES PETROMYZONTIDAE PETROMYZON TRIDENT ATUS. 377 



SYN. Petromyzonidae, BONTAP. Sagg. Distr. metod. Anim. Vertobr. 1831, 123. DEKAT, New Y. Faun. IV, 1842, 379. 



STOKER Synops. 1846, 265. 

 Petromyzontidae, OWEN, Lect. Comp. Anat. Vertebr. anim. 1846, 48. Bn. 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 (Pdromyzon and Ammoccctes) 

 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 

 the chest. 



SVN. Petromj/zon, LINN. Syst. Nat. ed. XlJa 1766, 394. GMEL. in Linn. Syst. Nat. ed. XIII a I, HI, 1788, 1513. DUM. 

 Zool. analyt. 1806; in Mag. Encyl. 1808 ; & Ichthyol. analyt. 1856, 112. Crv. Regn. anim. II, 1817, 117 ; 

 2d ed. 1829 ; & ed. illustr. Poiss. 380. STOKER, Rep. Fish. Mass. 1839, 195 ; &, Synops. 1846, 265. 

 DEKAT, New Y. Faun. IV, 1842, 379. 



The genus Petromyzon y 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, L. ; P. fluviatilis, L.; P. americanus, LESU. ; P. nigricans, LESU. ; P. tridentatus, 

 GAIRDN.; P. ciliatus, AYRES ; P, plumbeus, AYRES ; P. niger,* and P. borealis.^ 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. 



STN. Petromyzon tridentatus, GAIRDN. in Lit. : RICHARDS. Faun. Bor. Amer, Ill, 1836, 293. DE KAT,N. Y. Fauna, IV, 

 1842, 382. STOKER, 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 be 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 &quot;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,&quot; &c., are the base of 

 insertion of very small and acute teeth. The &quot; transverse row of four teeth&quot; 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. 

 ^Petromyzon Jluvialis, RICHARDS. Faun. Bor. Amer. Ill, 1836, 294. 



48 a 



