4 DEEP-SEA FISHES OF THE ATLANTIC BASIN. 



by a lip, and armed with dentigerous lamella- on its disk, as well as with lingual teeth; 

 enlarged plates above and below the antrum of the esophagus have been called maxillary 

 and mandibular, but they have no hoinological relation with the upper and lower jaws of 

 ordinary fishes, and the lower jaw in them is absolutely wanting. 



This order embraces only a single family of existing species (the Petromyzontidce or 

 lampreys), of which there are at least five genera, three of which are represented in North 

 America. (Gill.) 



Family PETROMYZONTIDCE. 



Petromyzontiila; GCntiiek, Cat. Fish. Brit. Mus., vm. 499. 



PETROMYZON, Artedi. 



Petromyzon, Artedi, Genera Piscium, 64.— Lixx.ec-, Syst. Nat., ed. x. 1758, 5; ed. xn, 1766, i. 394. 



Dorsal fins two, the second continuous with the caudal; maxillary teeth separate, 

 pointed, close together, not forming a crescent-shaped plate ; mandibulary plate with seven to 

 nine cusps; lingual teeth serrated, forming two crescent-shaped plates on each side. 



PETROMYZON MAKINUS, Lixn i I s. 



Petromyzon marinus, Lixx.i D8, Syst. Nat., ed. x, 1758, 230; ed. xn, 1766. 394. GOnther, Cat. Fish. Brit. 



Mus., vm, 501. 

 Peiromyzon americanus, Le Sueur, Trans. Am. Phil. Soe., i, 383. — Stoker, Hist. Fish. Mass., 251. 



Specimens of a Petromyzon apparently not specifically distinct from P. marinm, have 

 been obtained from several localities at considerable depths. The Fish Commission trawled 

 it off Cape Ann at station 189, in 85 fathoms, and at 192 in 100 fathoms, and also at station 

 946, off Marthas Vineyard (lat. 39° 5.')', Ion. 71° 14'), at a depth of 217 fathoms, and bottom 

 temperature of 17°. The occurrence of this form at so great a depth is interesting in con- 

 nection with the record of the following species, P. Bairdii. 



PETKOMYZON (Bathv.myzox) BAIRDII, Gill. 



Petromyzon (Bathymyzon) Bairdii, Gill, Forest and Stream, xxi. Ann. 30, 1883; Proc. U. S. Nat.Mus., vi, 

 1883, 254. 



This form of lamprey was described by Gill from a single specimen (Nat. Mus., No. 

 33311), obtained by the U. S. Fish Commission at station 2018 (lat. 40° 02' 00", Ion. 68 

 50' 30"), at a depth of 517 fathoms. No specific characters were mentioned except those 

 enumerated above under the generis-" diagnosis -'supraoral and intraoral plates or laminae 

 destitute of odontoid tubercles, the armature of the lamprey type being obsolescent."' 



The form is very closely related to Petromyzon marinus, bat the limits of generic and 

 specific variation in the Hyperoartia are by no means definitely agreed upon, and Gill's 

 identification of this specimen is accepted without comment or criticism. 



The following MS. descriptions, prepared in 1883, have been placed in our hands by Dr. 

 Gill: 



The head, from the snout to the first branchial aperture, is contained about seven times 

 in the total length, while the eye is intermediate between the snout and fifth branchial 

 aperture. The diameter of the eye is equal to one-fourth of the distance of the interorbital 

 area. 



The diameter of the circular disk equals the interval between the eye and fifth branchial 

 aperture; the margin is regularly fringed, as in the related species. 



Indications of eight teeth are on the infroral lamina, and the tips of the two suproral 

 ones are barely perceptible; the pectinations of the lingual teeth are well marked and 

 differentiated. 



The chest (i. e., space between first and seventh branchial apertures) is about as long 

 as the snout. 



The fins are moderate, the anterior dorsal being somewhat higher in front of the middle 

 than the diameter of the orbit, and the second dorsal about twice as high or equal to the 

 distance between the eye and first branchial aperture. 



