406 



JSCAXniNAVlAN FISHES. 



two other grcjups, l)ut in tlie (litterentiatioii of its forms 

 is so little advanced tlint Ixitli these varieties luay also 

 be ranged as interiuediate forms between two species 

 of one of the otlier groups". The first group must, 

 tlierefore, stand nearest the presumal)le original type 

 of all three groups, unless, indeed, it may l)e shown 

 tliat it is tliat original type. 



When LiLLJEBOKG first disco\-ered his Flafessa dri- 

 i/ei/sis, he suspected tliat it was identical in species with 

 I'ai.las's Plenronecfes ciaifricosiis: and in this suspicion 

 lie was undoubtedly right. In another passage'' we have 

 combined this species with Stouer's Flafessa glabra : but. 

 the collections of the Vega Expedition prevent us from 

 following Jordan and Gilberts example', and unre- 



servedly uniting into one single species the two species 

 described I)v Pallas, /'/. i/Iacialis and /'/. cUafiicosus. 

 Pallas based his distinction between tliese species chiefly 

 on the deeper form of the body and the closer scaly 

 covering of I'lcitronccfcs f/lacialis. This ditt'erence re- 

 appears, even though it is moditied l)^- ditt'erences of 

 age and sex, Iietween the specimens of /'/. f/hicialls 

 brought home l)v NordkxskiOld's Expedition of 187") 

 from Chabarowa and bA- the \ ega Expedition from 

 Najtschkaj (N.E. Siberia) and the numerous examples 

 of 7V. cicafricosKS brought lioine bv LieutciLant Sande- 

 berg from Archangel. According to these collections 

 the followins" distinctions are valid: 



7V. (/laci'ilis 

 fr. Najtschkaj. 



Greatest depth of the body in % of the lenijth of tlie body .' > 41 (Average: 43.9) 



Length of the head iii % of the greatest depth of the body < 57'' (Average: 5Lo) 



Postorbital length of the head in % of the greatest depth of the body < SS"" (Average: 35.51 



Length of the head in % of the greatest distance between the lateral line and the ventral edge < 93'' (Average: 8().3) 



I'l. cicntr/f'Oii'fs 

 fr. Archangel. 

 < 41 (Average: 39.2^ 



> 57'' (Average: 01,7) 



> 40" (Average: 42.5) 



> 93 (Average: 101. (! I 



Although these differences are not great, and al- 

 though, considering the variability of the kindred spe- 

 cies, they seem rather to belong to varieties, still they 

 exist, to judge by 9 specimens of PI. gJariaJis and more 

 than 20 of J'l. ckafricosus: and so long as a character 

 ])roves tenable, we have no right to reject the distinc- 

 tion l)ased on it, wliethcr we choose to regard tlie latter 

 as a distinction of species or merely of Aariety. As is 

 generally the case in the Scandinavian Flatfishes, the 

 females are in the majority, and this to such an extent 

 that we have not found a single male among the spe- 

 cimens of I'L ckatricosiis. However, this does not af- 

 fect the significance of the differences given here, as 

 it is by the shallower (narrower) form of the body 

 that the males are externally distinguished, and in PI. 

 cicatricosus they \voidd thus oidy liave still further di- 

 minished the average depth of the bod}-. 



Pallas obtained his Plciironerfes cicatricosus from 

 the basin of the Pacific^ and PI. c/Jacialis from Kara 

 Sea and the Gulf of Obi'; and it would tlius appear 



that the former belonged to the cast, the latter to the 

 west, of the Arctic Ocean and the ()ld World. But 

 we have no recorded observation of J'l. glaciaHs west 

 of Nova Zembla, while PI. cicatricosus, on the other 

 hand, must be recognised as common in the White Sea. 

 According to Guntiier's description" of the type-spe- 

 cimen of Kiciiardsgn's pi. f/Iacia1is, from Batluirst Inlet 

 (the middle of the Arctic coast of North America) this 

 specimen really belongs to the form thus entitled by 

 Pallas. On the other hand, tlie Alaskan species de- 

 scribed under this name bv Jordan and Gilbert and 

 figured by Todd'', evidently possesses the characters of 

 PI. cicatricosus, of the occurrence of which on the Arctic 

 coast of North America east of Alaska we have no re- 

 corded observation, though it is common and kno'wn by 

 the name of Christmas-fish at Salem, on the Atlantic 

 coast of the United States. The latter species is just 

 as. little known to the north of Asia, west of Behring 

 Strait. In its geographical range there thus appear, as 

 far as we know at present, three great gaps, the first 



" LiLLJEBORG also says of his Platessa dcinensis: "It seems td be an intermediate form between Plat, vulgaris and Plat. ^riesiiK. By 

 the structure of the teeth it is approximated to the former, and by the covering- of tlie body and tlie coloration to the latter." 



*• Ur vai' ticls forshning (Retzius), No. 29, p. 59. 



' Bull. U. S. Nat. Mus., No. 16, ji. 837. 



'' An exceptional case. 



' "Specimina e mari inter Camtschatcaiii et Aniericam Iccta milii retulit D. D. Mehk." 



■' "In iittoribus vadosis maris glacialis ad Sinuni Carensem et Obi fl. ostia legit Bash, Su.tee." Chabarowa, where Norpekskiulp's Ex- 

 pedition of 1875 found PL glacialiK, lies off Jugor-scliarr, just at the division between Kara Sea and the Munnan Sea. 



f Brit. Mus. Cat., Fish., vol IV, p. 442; Pleuronectes Franklinii. 



'• Br. Goope, Fish.. Fi.-<h. Imhtstr. U. S., sect. I, pi. 47. 



