1180 



SCAXDIXAVIAN FISHKS. 



back in the young". Tliu length of the tin is about 

 9', 2 — 12 % of that of the l)ody. The second dorsal is 

 considerably higher (sometimes twice as high or a little 

 more), but essentially of the same form, its length 

 varying l)etween about 18 and i^ % of that of the 

 body, with the highest percentage in old specimens. 

 Behind it meets the caudal fin, or overlaps the u])i)er 

 anterior margin thereof, but is always sharply defined, 

 as well as the first dorsal, at its jjosterior termination. 

 Ill front it is separated tVoni the first dorsal b)' an in- 

 ter\al which in adult specimens (over 2'/2 dm. long) 

 varies with age from about (i to 4 % of the length of 

 tlie body, and wliicli, according to Wilder's measure- 

 ments of tlie North American fresh-water form, is less 

 in the males than in the females. Tlie diphycercal 

 (almost symmetrical) caudal fin is uniformly widened 

 behind (tongue-shaped), with short, triangular but 

 rounded tip. The entire length of the caudal fin oc- 

 cupies in adult Lam]>reys about 9' j — S'/a % of the 

 length of the liody. 



The anal aperture lies below the anterior portion 

 of the second dorsal fin, at a distance from the tip of 

 the snout measuring 75'' — 72 % of the length of the 

 body, further back in the young than in the old. The 

 urogenital papilla is comparatively small. As men- 

 tioned above, all the Cyclostomes are without anal fin; 

 but between the vent and the caudal fin a dermal carina 

 frequently occurs, similar to that of the dorsal margin. 



The coloration varies with age, locality, and the 

 time of year. Our figure represents a nearly ripe fe- 

 male in a fresh condition, as recei\ed by the Royal 

 Museum from Ringkjobing (Jutland) at the end of May 

 through Mr. <J. Fredericksen. Here oidy tlie wliite 

 and lilue colours prevailed, the former being pin-e on 

 the belly, the latter pale but unmixed on the head, and 

 composing tlie pale gi'ound-colour of the sides and liack, 

 ^^•hich were mottled with a darker blue, siiading into black. 

 The fins were pale, mottled with blue, with a dash of gray. 

 The pupil was black, the iris of a faint silvery lustre 

 but not much jjaler than tlie pre\ailiiig colour. Tlie 

 gill-openings and mouth were tinged with red. Ooxo- 

 van' figui'es and describes the species as more varie- 

 gated, with a ground-colour of lustrous green, mingled 



with blue, yellow, and red, \\ith a handsome marbling 

 of Idack. He also adduces blue and olive varieties, as 

 M'ell as reddish ones mottled with chestnut-brown in- 

 stead of black. According to Kroyer the under surface 

 of the head is yelloM-, the fins being reddish, of a dark 

 orange, the dorsal fins besides mottled with black. Ac- 

 cording to both ilALM and CoixETT the marbling is 

 absent in young specimens; and according to Lesleur 

 and Dekay this also apjdies to the lar\:e. 



The larval stage, so far as is known, has not yet 

 been observed in Europe; but in North America an 

 Ammocn'tes hiiolor was described })y Le.sueur (1818) 

 and another form, Amm. nmcolor, by Dekay (1842), both 

 of ^vhich have been referred by Jordan and Fordice to 

 Petromijzon marhrus as its larvie. The former of these, 

 according to Dekay', has not been rediscovered since 

 Lesueur's time, but had lieen named from its colora- 

 tion, reddish on the liack and sides, white on the belly, 

 with a sharp, undulating limit between these U\o co- 

 lours. The latter {Hiiicolor) is in all respects still more 

 like an earthworm, but has developed distinct eyes. Its 

 coloration is described by Dekay as a nearly uniform 

 dark or dusky brown, occasionally verging to bluish, 

 somewhat lighter beneath; the anterior ]>art of the head 

 darkest. The form of the body cylindrical for Uvu 

 thirds of its length from the head, becoming slightly 

 compressed just anterior to the vent, very much com- 

 pressed and acuminated at the tail. Greatest depth of 

 the body 7'/2 % of its length. Surface smooth, with 

 between 80 and 90 transverse folds (myocommata), 

 giving tlie body an annulated appeai-ance. The fins ap- 

 pear to lie nothing more than mere membranous pro- 

 longations of the skin, without the slightest \estige of 

 rays. The dorsal commences at the beginning of the 

 3rd fifth of the length of the liody (from the snout), in 

 a scarcely perceptible furr^)^v. and advances low and 

 subequally until about the middle of its length, when 

 it begins to rise, and then rapidly diminishes at the tij) 

 of the tail, where it unites with the caudal and anal, 

 which latter is obsoletely triangular, and becomes in- 

 sensibly effaced at a point corresponding to the begin- 

 ning of the last fourth of the length of the body. The 

 vent is a large longitudinal aperture between the 2nd 



" (Uir measurements of S(ia Lampreys 2'/.2 — 8')., dm. long show that tlio distance from the tip of the snout to the heginning of the 

 first dorsal tin diminisiies with increasing age from 53 to 48 % of the lengtli of the l)ody. Kboyer's measurements of specimens 4 — S'/j 

 dm. long indicate that tliese percentages decrease from 51' o to 50. 



'' According to Meek (1. c.) exceptionally 77 or even 80. 



'■ Brit. Fish., pi. LXXXI. 



