4 DEEP-SEA FISHES OF THE ATLANTIC BASIN. 



by a lip, ami aniu'd with dentigerous laincllif on its disk, as wi'll as with lingual teeth; 

 eulaif^ed plates above and below the antrum of the esophagus have been ealled maxillary 

 and mandibular, but they have no homoh)gical ielati(m with the upper and h)\ver jaws of 

 ordinary fishes, and the lower jaw iu tliem is absolutely wanting. 



This order embraees only a single family of existing speeies (the Pciromyzontidw or 

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

 America. (Gill.) 



Family PETROMYZONTID^E. 



Pctromysontida', Guntiikh, Cat. Fish. Brit. Mus., viii, 4'j;t. 



PETROMYZON, Artedi. 

 retromyzon, Artkdi, Genera Piscium, 64.— Linn.el'S, Syst. Nat., ed. x, 1758, .5; ed. xil, 1766, i, 394. 



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

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

 uinecu.sps; lingual teeth serrated, formiug two crescent-shaped plates on each side. 



PETROMYZON MARINUS, Linn.eis. 



retromyzon mariniis, Lixn.eus, Syst. Nat., etl. x, 1758, 230; ed. xii, 1766, 394. GCxthek, Cat. Fish. Brit. 



Mus., VIII, 501. 

 Pctromyzon umerkanus, Le Sieuk, Trans. Am. Phil. Soc., i, 383.— Storer, Hist. Fish. Mass., 251. 



Specimens of a Petromyzori apparently not specifically distinct from P. 7iiarinus, 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 

 916, off Marthas Vineyard (lat. 39° 55', Ion. 71° 11')? at a depth of 247 fathoms, anil 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 (Bathymyzon) BAIRDII, Gill. 



Pelromyzon {Bathymyzon) 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 (Xat. Mus., No. 

 33311), obtained by the U. S. Fish Commission at station 201S (lat. lOo 02' 00", Ion. (iso 

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

 (Miumerated above under the generic diagnosis "supraoral and intraoral plates or laminae 

 destitute of odontoid tubercles, the aruiature 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 upon, and Gill's 

 identifi(;ation 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 distam^e of the iiiterorbital 

 area. 



The diameter of the circular disk eipials 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 sujiroial 

 ones arci baiely i)erceptible; the pectinations of the lingual teeth are well marked and 

 ditferentiated. 



The chest [i. e., space betw-een first and seventh branchial apertures) is about as long 

 as the snout. 



The fins are moderate, the anterior dorsal being somewhat higiier iu front of the middle 

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

 distance between the eye and first branchial aperture. 



