12 Bulletin 47, United States National Museum. 



lamprey, found in the North Pacific, similar in habit to Petromyzon marinus 

 of the North Atlantic, (gvrdf, within; a<j>rfv, wedge; the lingual tooth 

 being wedge-shaped.) 



11. ENTOSPHENUS TRIDENTATUS, (Gairdner). 



Lips thick, fringed with numerous papillae, within which are small 

 teeth. Infraoral lamina with 5 or 6 cusps ; buccal teeth before mouth 

 unicuspid, those on sides larger, the first and last bicuspid, the middle 

 ones tricuspid ; median supraoral cusp little more than i the length of 

 the other 2 ; first dorsal fin distant about f of its own length from the 

 second. Head 8 to 10 in length ; 73 muscular impressions between gill 

 openings and vent. Color, plain dark brown, rarely mottled. Pacific 

 coast of America, Unalaska to Southern California; ascending streams to 

 spawn, going as far as Walla Walla, in the Columbia, its range southward 

 extends to Santa Ana River at Riverside, California. L. 18 inches or 

 more, (tridentatus, three-toothed.) 



Petromyzon tridentatus, (GAIRDNER MS.), RICHARDSON, Fauna Bor. Am., 293, 1836, Falls of the 

 Walamet, now Willamette. 



Petromyzon cilialm, AYRES, Proc. Cal. Ac. Sci., 1855, 44, San Francisco. 



Petromyzon lividus, GIRARD, Pac. R. R. Surv., 379, 1858, Wahlahmath River, Oregon (Willa- 

 mette River.) (Type, No. 976.) 



Petromyzon astori, GIRARD, I. c., 380, 1858, Astoria, Oregon. (Type, No. 978.) 



Ichthyomyzon tridentatus and astori, GUNTHER, Cat., vm, 506, 1870. 



Entosphenus epihexodon, GILL, Proc. Ac. Nat. Sci. Phila., 1862, 331, Fort Reading, California 

 after Girard. 



Lampetra tridentata, aslori, and epihexodon, JORDAN & GILBERT, Synopsis, 7, 8, 1883. 



Ammocceles tridentatus, JORDAN & FORDICE, /. c., 291, 1886. 



9. LAMPETRA,* Gray. 

 (BROOK LAMPREYS.) 



Lampetra, GRAY, Proc. Zool. Soc. London, 1851, 235, (fluvialis). 



Lampreys of small size, with the dorsal fin emarginate or divided into 

 two parts, the posterior portion continuous with the low anal fin around 

 the tail ; supraoral lamina broad, forming a cresceutic plate, with a large 

 bluntish cusp at each end, and rarely a very small median cusp; lingual 

 teeth small, with a crescent-shaped dentate edge, the median denticle 

 enlarged ; buccal disk small, its teeth few nd never tricuspid. Small 

 lampreys, inhabiting the brooks of Europe and North America. Five or 6 

 species known, bearing much the same relation to Entosphenus that Ichthy- 

 omyzon bears to Petromyzon. (lambere, to suck; petra, stone.) 



. Dorsal fin divided into 2 parts which are separate, or joined at base only. 



* The name AmmocoRtes was originally applied to the larval forms of Petromyzonids which are 

 in that stage specifically indistinguishable and which were supposed by Dumeril and Cuvier to 

 be generically distinct from the adult forms. After the identity of the two was discovered, the 

 name Ammocceles was used by many writers, following a suggestion of Milne-Edwards, as a gen- 

 eral term to be applied to the blind or larval stage of all lampreys. Lampelra of Gray should 

 therefore be used for this genus, for which it was originally proposed. Inasmuch as no Euro- 

 pean Ammocaetes can be referred to any determinate species of Peiromyzonid, the nominal genus 

 corresponds with Petromyzon^ a whole and not to any subdivision. 



