1. PFIROMYZON. 503 



p. 41, taf. 78. fig. 1 ; Bl Schn. p. u:;0; Donov. Brit. Fish. pi. 80; 



Pall. Zoof/r. liuss.- As. i'li. \^. V)ij ; Ekstrmn, Fische iT/w7w, p. 2()7 ; 



Firm. Brit. An. p. 404 ; Jeiiym, Man. p. 521 ; Parn. Fish. Firth of 



Forth, p. 284; Yarrell, Brit. Fish. 2ud edit. ii. p. 598, or, 3rd 



edit. i. p. 28 * ; Nihs. Slcand. Faun. Fish. p. 745 ; Richards. Faun. 



Bor.-Amer. Fish. p. 294 ; Si'lys-Lonuchamps, Faune Bch/e, p. 220 ; 



Kriiyei; Damn. Fish. iii. p. 1042 ; Giinth. Fisch. Ncchars, p. loJ ; 



Ileckcl 8,- Kner, SUsswasserf. p. 'All, tig. 202 ; Auf). Midler, in 



Miiller's Arch. 1856, p. 325; Siebold, SUsswasserf. \^. '•'>7'2 ; Gronov. 



Sy.st. ed. Grai/, p. 1 ; Bhinchard, Puiss. France, p. 515; Vanestrini, 



Arch. p. la Zool. iv. p. 185. 

 Lamperu, l\'nn. Brit. Zuol. iii. p. 100, pi. 10; Couch, Fish. Brit. Isl. 



iv. p. 305, pi. 247. fig. 2. 

 Petromyzon argenteus, Bl. taf. 415. tig. 2 ; Bl. Schn. p. 532, tab. 102. 



fig. 1 ; Couch, I. c. p. 400, pi. 247. fig. 3. 



pricka, Laccp. i. p. 18. 



jura;, MacCulloch, West. Isles, ii. f. 18G,pl. 29. 



nigricans, Lesueur, Trans. Am. Plal. Soc. i. p. 385 ; Storcr, Mem. 



Amer. Ac. ix. 1867, p. 253, pi. 39. fig. 6. 

 Lampetra fluviatilis, Gray, Chondropt. p. 140, or Proc. Zool. Soc. 1851, 



p. 237, pi. 4. fig. 2. 

 Petromyzon omalii. Van Beneden, Bull. Ac. Sc. Bely. ii. 1857, p. 549, 



figs, i-3, and xx. 1865, p. 46 ; 3Ialm, ForhandL Skand. ntrf. 8de 



mode. Kjobenli. 1860, p. 580. 

 Organ of hearing: Owyannikow, Mem. Ac. Sc. St. Petersh. viii. 1864. 



Maxillary tooth single, forming a transverse ridge with a cusp at 

 each end ; mandibiilary tooth single, crescent-shaped, with about 

 seven cusps. Tongue with a broad, transverse, trenchant tooth, which 

 is provided with a median cusp. Two or three bi- or tricuspid teeth 

 on each side of the gullet ; the other teeth of the suctorial disk arc 

 small and not numerous. Pirst dorsal fin separated from the second 

 b}' an interspace. Coloration immaculate ; sides silvery. 



Coasts and rivers of Europe, North America, and Japan. 



(/, b,c-d, e-f. Adult and half-grown. England. 



//, 7t, i, 1--1. Adult. Holland. 



m-q. Adult. Belgium. Presented by Prof, van Beneden as P. 



omalii. 

 r. Ten inches long. North America. Purchased of M. Parzudaki. 

 s. Nine inches long. Eussian North America. From II r. Grubcr's 



Collection. 

 I am indebted to Prof, van Beneden for the opportunity of com- 

 paring specimens of his Z'. 0)))rtZ/(' with examples oi P.JJuvintihs from 

 Holland, England, and other countries, and have come to the conclu- 

 sion that there is no specific difference between them. Tliis may ai>- 

 pear a matter of surprise to those who, without specimens, consult 

 the description and figure given by Prof, van Beneden. He repre- 

 sents the new species as finless, but in the examples sent the fins arc 

 well developed, and of exactly the same shape and position as in P. 

 fhiviafiUs. With regard to the dentition, P. omalii is represented 

 "with ten points to the mandibular lamina, and without small teoth 



* Figure of dentition ineorrcet. 



