4 DEEP-SEA FISHES OF THE ATLANTIC HASIN. 



by a lip, and armed with deutigerous lainelhie cm 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 homological rehitiou with t lie 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 retromnzojitidw or 

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

 America. (Gill.) 



Family PETROMYZONTID^^. 



Petromyzontidce, Guntukh, Cat. Fish. IJrit. Mus., viii, 4;i;t. 



PETROMYZON, Arledi. 



reiromiizon, Artedi, Geuera Pisoium, 6-1. — Linx.euis, 8yst. Nat., etl. x, 1758, 5; eil. xil, 176G, i. 304. 



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 MARINUS, Linn.eus. 



Fetromyzon marinm, Lisn.eus, Syst. Nat., ed. x, 1758, 230; ed. xii, 17G6, 394. GCxtheu, Cat. Fish. Brit. 



Mas., vili, 501. 

 Petromyzon amcricnnitK, Lk Sueue, Trans. Am. Phil. Soc, i, 383.— Stoker, Hist. Fish. Mass., 251. 



Specimens of a Petromyzon apparently not specifically distinct from P. mnrinus, 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, ami also at station 

 9i6, off Marthas Vineyard (lat. 39° 55', Ion. 71° W), at a depth of 1!47 fathoms, and bottom 

 temperature of 47°. The occurrence of this form at so great a depth is interesting in con- 

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



PETROMYZON (B.\thymyzon) BAIRDII, Gill. 



rdromyzoH (Bathymyzun) Bairdii, Gill, Forest and. Stream, xxi, Aug. 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 UOIS (lat. 40^ oi" 00", Ion. 08° 

 50' 30"), at a depth of 547 fathoms. No specific characters were mentioned except those 

 enumerated above under the generic diagnosis "supraoral and intraoral plates or lauiime 

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



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

 specific variation in the Hyperoartia are by no means definitely agreed ui)oii, 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 liauds by Dr. 

 Gill: 



The head, from the snout to the first branchial aperture, is contained about scncii 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 intcrorbital 

 area. 



The diameter of the circular disk ecjuals the interval between the eye and tilt li branchial 

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



Indications of eight teetli are on the infroral lamina, and the tips of the two sujiroral 

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

 differentiated. 



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

 as the snout. 



The fins are moderate, the anterior dorsal being somcwiiat higlicr in liont of tlic niichlle 

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

 distance between the eye and first branchial aperture. 



