AMMIIDVTID.K. 



57; 



lliis r('lati\c l('iii;'lli (Iccrcascs with incrcfisin^' age, and 

 in this respect Am. hincedlutiis thus )'utaiiis a ju\('iiile 

 character. Nor can tiie ciiaracfer l)e eni]ii()\e(l as a- 

 specific distinction, tor in a younii' .speciuieii of the Saiid- 

 Laiince .')() mm. long, taken by Fries in BohusIiVn, the 

 lengtli of the head is nearly 21 % of that of the body. 

 Ill tlie same specimen tlie length of tlie lower jaw is 

 I)'.') "/ of that of the body, while in other I'ases the 

 b()undar\' between the speties in this respect lies at 9 %. 

 Tlie length of the pectoral tins, where the line of di- 

 stinction is the same, but tlie direction of distinction 

 reversed — X\\v ]}ercentage less in Am. laiicculafKs tiian 

 in Am. tohkuuts —in a specimen of Am. toliiaiiiis 20 

 cm. long is only 9'1 % of the length of the body, and 

 in a specimen of .im. lanceolatiis 11 cm. long 9 ^ of 

 tlie same length. In this respect, too, the percentages 

 decrease with increasing age, and in tliis respect Am. 

 tohianiis thus retains a juvenile character. In his de- 

 scription of Ammoihites americanus" Stoker says the 

 dorsal tin liegins just at the end of the pectoral fin, 

 and that the length of tlie latter tin is only ^Is of that 

 of tlie heail. It was by this statement that I was in- 

 duced to refer the Sand-Eols brought home by the Vega 

 E.xpedition from Pitlekaj, north-west of Behring Strait, 

 to Am. laiuea, nir. umericana'', for in a specimen 77 

 mm. long the beginning of the dorsal tin lay at a 

 distance from the tip of the snout measuring 29"3 % of 

 the length of the body, and extremely little in front 

 of the tip of the pectoral tin, though this fin measured 

 1 1 % of the length of the body. Later investigations, 

 however, especially those of Jouoax and Giliseht, show 

 that Stoker's description and figure must have been 

 based on some exceptional specimen, for, unless this 

 were so, such a character could not have escaped ob- 



serxatioii. Still, this sliows that even the characters 

 most important in a systematic respect are subject to 

 variation. According to Stcjukr Am. amcriccnius may 

 also attain a size of M dm., though from a specimen 

 which the Royal Museum has received through the 

 Smithsonian Institution from ^^'oods Hole (Mass.), it 

 apjiears to be (piite identical with A))i. fdhidiiiis. The 

 other two American species that have been ranged be- 

 side Dekav's ^i)iim(i{li/tps (niierirainis', but which are 

 regarded by Jordan and (iilbekt merely as varieties 

 of this species, show among their characters a variation 

 of the transverse dermal folds on the sides of the body 

 between 130 and 1<S2, thus tilling the gap between the 

 normal numbers in Am. toJnanus and Am. lanccoJafus, 

 and showing how the form-differentiation may bring 

 about a resemblance to Am. Janceohttiis, without altera- 

 tion in the structure of the mouth and without the 

 development of teeth on the head of the vomer. The 

 development of the said dermal folds, the absence of 

 which is one of the most ini|)ortant cliaracters of Am. 

 cicerehis, in Am. fubianus is a. character of growth ex- 

 tremely irregular in its appearance. Y.xen in specimens 

 7 cm. long it is sometimes impossible to discover them. 

 Of the other character which should serve to distinguish 

 Am. cicerehis, the undulating margins of the dorsal and 

 anal tins, I have found at least a trace in a slight con- 

 cavity of the margin of the anal tin in a young Sand- 

 Launce. All this goes to show, not only that all the 

 species are extremely closely related — so closely that 

 we may well lie tempted to regard them merely as 

 varieties of the same species, or as species at the be- 

 ginning of their differentiation from each other — but also 

 that this relationship has its origin in a form essentially 

 resembling Am. tohiaiiits, or perhaps in this very species. 



At least one of the species descrihed ab(>^•e, the 

 Sand-Launce, must be regarded as circumpolar. The 

 Royal Museum })Ossesses examples of this species from 

 Norwegian Finmark, the Murman Coast, the White Sea, 

 North-East Siberia, Greenland, and Iceland. In Spitz- 

 bergen, however, it is unknown. According to Machado 

 (([uoted by Steixdachxek) the range of this species 

 extends southward to Cadiz. Day assumes that it may 



occasionally wander into the Mediterranean; but he gives 

 no observation of its occurrence there. In the Baltic 

 the Sand-Launce penetrates at least to tlie island-belt 

 of Stockholm and, according to Mela, to the islands 

 round Aland and Abo and into the Gulf of Finland 

 up to the island of Hogland. In the first locality Sux- 

 DEVALL could iiot tiiid it; but during the investigations 

 which I caused to be made this summer (August, 1890) 



" Mem. Amer. Aeail. Arts, Sc. n. ser., vol. VIII, p. 411, pi. .XXXIII. tig. 2. 

 *■ Gt. Intern. Fisher. Exliib. Loiidou 1883, Swed. Spec. Catal.. p. ITD. 

 ' Girard's Ammodytes personatus and Cope's Am. alascanus. 



