1. I'lnitojivzox. 501 



Petromyzon et Lampctra, (rra;/, Vhumlnipt. p. 1-J-".. 



Larva: Amraoccetos, (I)iiriieril) Cuv. lih/ne An. 



Larva : Scolecosoina, (Uranl, U. <S'. Pat: R. li. Lxped. Finh. p. 8ci4. 



Dorsal tins two, the posterior continuous with the caudal. The 

 maxillary dentition consists of two teeth placed close together, or 

 of a transverse bicuspid ridge ; lingual teeth serrated. 



Coasts and fresh waters of the northern hemisphere. 



Prof. Aug. Miillcr (Miiller's Archiv, ISoG, p. '.i-Jo) has sLuwn 

 that the Hshes of this genus are subject to a metamorphosis, the 

 larval form having hecn hitherto known as Ammocoetes. He has 

 proved the truth of his discovery by tracing the dcvi'lopment of 

 Ammoceetes branchialis into Petroinijzon planeri. It maj'lie assumed 

 that not only the Petromyzons proper, but also the lishes of the 

 allied genera undergo a similar metamorpliosis. 



Ammocoetes branchialis I'equires three or four j'cars for its com- 

 plete development. In the larval state the head is very small, and 

 the buccal cavity is surrounded by a semicircular upper lip, the 

 separate lower lip being very small. There are no teeth, but several 

 fringed barbels surround the mouth. The eyes are extremely small, 

 hidden in a shallow groove. A median single nasal opening and 

 seven gill-openings, as in the adult. The vertical fins form a con- 

 tinuous fringe, in which the later di^■isions are more or le.ss dis- 

 tinctly indicated. Species described as Ammocoetes and distinguished 

 by their authors on account of modihcations of the organs subject to 

 metamorphosis, are, of course, quite inadmissible. 



On the numerous publications on the anatomy of the Lampreys, 

 consult Engelmann & Carus, Biblioth. Zoolog. pp. 1030-1031. 



1. Petromyzon marinus. 



The Sca-Iianiprey. See-Xeunauge. Lamproie. Xejouogon (Sivcd.). 



Lampetra s. Mustela, Bvllon. IJe Aqiuit. p. 70 ; Bomlel. p. .398 ; 

 WiUiujhly, p. lOo, tab. 2. fig. 2. 



Lampetra maculosa, Salvian. f. (S?> a. 



major, Salvian. f. 08 h; Aldrov. p. 589 ; Jon^ton. De Pise. tab. 



24. f. 0. 



Petromyzon, sp. uo. 2, Artedi, Si/mvi. p. 90 ; Gcii. p. 04. 



Petromj'zou marinus, L. Si/st. Nat. i. p. 804; Xau, Schrift. Ges. 

 ntrf. Frcund. licrl. vii. p. 4!i0; Sclnvpff', Schrift. Cc.i. iitrf. Frcuud. 

 Berl. viii. p. 184; Bl. Fisch. Dcutuhl. iii. p. 8S, taf. 77; Bl. &hn. 

 p. 6.30; Lacrp. i. p. 8, pi. 1 ; .Mitch. Lit. .V Phd. Traits. Xcic York, 

 1. p. 461; Domn: Brit. Fish. pi. 81; Flem. Brit. An. p. ]fi8; 

 Miille.r, AhhnmU. Ak. Jfrn. Berl. 18:U, p. 78; Panwll, Fi.^h. Firth 

 of Forth, f. ■lf<-2 : Yarrcll, Brit. F/.s/(. 2nd edit. ii. p. oOS, or, 8rd 

 edit. i. p. 82 ; Gray, Chondropt. p. 188, or iVoo. Zool. Soc. 1851, 

 p. 235, pi. 4. fig. 1 ; A7/.<--. Shaiid. Faun. Fi'<h. p. 74.> ; Seli/s-Lontjvh. 

 Faun. Bclffc, Tp. 22^} ; Kroi/cr, Danm. Fisk. iii. p. 102.j ; Giinfh. 

 Fisch. Xcckars, Y>. 181; Ileekcl •$■ Kner, SiLfswa^'crf. p. .374, figs. 

 200 & 201 ; Sicbo/d, Siis.vra<.scrf. p. 808 ; Bert, Ann. AV. .V«/. 18(!7, 

 vii. p. 871 ; Blanchard, Poi^s. France, p. 512; Cancstrini, Arch. p. 

 hi Z'lol. iv. p. 184. 



