Jordan and Kvcrntiinn. Fishes of North America. 



tld. Anterior lingual tooth divided by a median groove; dorsal fin continuous, 



with ;i broad notch. Small lampreys; fluviatile. ICHTHYOMYZON, 7. 



<>*. Snpraoral lamina very largo, expanded laterally, forming a crescent-shaped plate 



with a cusp ;it cither end and sometimes a median cusp; anterior lingual teeth 



more or !>>ss serrate. 



i'. Snpraoral lamina with a well-developed median cusp; anterior lingual tooth 

 wedge-shaped, its edge finely serrate and nearly straight ; dorsal fin divid- 

 ed ; Imncal disk moderate, some of its teeth bicuspid. Largo lampreys; 

 anadromous. ENTOSPHENUS, 8. 



ee. Snpraoral lamina with a very small median cusp or none; anterior lingual 

 tooth little developed, its edge crescent-shaped and dentate; the middle 

 denticle enlarged; Imcoal disk small, the teeth small and never tricuspid; 

 dorsal fins separate or deeply divided; small lampreys; fluviatile. 



LAMPETRA, 9. 



5. BATHYMYZON, Gill. 



Iiat)i>/i>iir.n, GILL, Proc. U.S. Nat. Mus., 1883, 254, (bairdii). 



Supraoral lamina contracted, its two converging teeth almost completely 

 fused, and only evident at the summit of the combined mass; infraoral 

 lamina crescentiform and spout-like at the middle and with the den- 

 ticles obsolete; discoperipheral teeth numerous and in obliquely arched 

 series of 4 to 7, declining downward ; innermost lateral teeth of the 4 rows 

 diverging from mouth, in each side bicuspid, with the cusps approx- 

 imated and diminishing downward rapidly; lingual teeth 3, pectinate, 

 the anterior deeply impressed and silicate backward at the middle, and 

 the posterior correspondingly curved backward at their inner lateral 

 angles ; the anterior dorsal fin distinct from posterior, (fia&vc, deep ; 



,///xw, to suck.) 



7. BATHYMYZON BAIRDII, (Gill). 



Head from snout to first branchial aperture about 7 times in total 

 length ; eye midway between snout and fifth branchial aperture ; diame- 

 ter of buccal disk equal to interval between eye and fifth branchial aper- 

 ture, the margin regularly fringed ; indications of 8 teeth on the infraoral 

 lamina ; tips of the two supraoral ones barely perceptible ; pectinations 

 of lingual teeth well marked. Chest about as long as snout. Fins mod- 

 erate ; anterior dorsal somewhat higher in front of middle than diameter 

 of orbit, second dorsal about twice as high, or equal to the distance be- 

 tween eye and first branchial aperture. Color dark, belly grayish ; second 

 dorsal darker across middle in front and toward margin behind ; caudal 

 blackish throughout. (Gill.) Gulf stream, once taken. (Named for 

 Spencer Fullerton Baird.) 



P>-1i-<:i,iii-.:n (J!ii/l,//,,iii~on) lairdii, GILL, /. c., 254, 1883; lat. 49 N., 547 fathoms; GOODE & 

 BEAN, Oceanic Ichthyology, 4, 1894. (Type, No. 33311.) 



6. PETROMYZON, (Artedi), 'Linnaeus. 

 (LAMPREYS.) 



Petromyznn, (ARTEDI), LINNAEUS, Systema Xatnra?, Ed. x, 1758, 230 (marinu*). 



Asmooodn\ (Dnnu'-ril), CUVIER, Regne Animal, Ed. i, 119, 1817, (branchial!*, larval form of any 



or all European species.) 

 Ammoc(?lns, BI.AIXVILLE, Faune Francaiso, liv. xxiv, 3, 1828, (branchialis). 



Lampreys with the supraoral lamina armed with 2 or 3 separate teeth, 

 pointed, and close together, not forming a crescent-shaped plate ; anterior 



