pleuronectin;e 295 



each jaw, more or less enlarged anteriorly ; vomer toothless. Gill-rakers rather long 

 and slender, in moderate number ; lower pharyngeals narrow, scarcely approximated 

 anteriorly, each with two irregular series of teeth. Dorsal fin with 67 to loi rays, 

 commencing just behind nostrils of blind side and above anterior part of eye ; anterior 

 rays not free ; all the rays simple, mostly scaled on ocular side. Tip of first inter- 

 haemal spine projecting in front of anal fin, which has 51 to 79 rays. Pectoral fins 

 unequal, that of ocular side a little larger ; all the rays usually simple. Pelvic fins 

 short-based, subequal and subsymmetrical. Caudal fin with the middle rays longest ; 

 caudal peduncle of moderate length. Scales small, adherent, ctenoid or cycloid ; 

 supplementary scales not usually developed. Lateral line rising slightly or with a 

 low cur\-e above the pectoral fin. Vent median, between the pelvic fins ; 3 + 1 

 pyloric appendages. Vertebrae 42 to 45 (13 + 29 — 32). 

 Four species from the North Atlantic and North Pacific. 



Synopsis of the Species and Subspecies. 

 I. 8 branchiostegal rays ; lateral line nearly straight ; contours of posterior 

 parts of dorsal and anal fins (at least in adults) more or less convex 

 [Atlantic species] . . . . . . . .1. platessoides. 



A. Depth 2 J to 2f in length ; maxillary 2j to nearly 3, lower jaw 2^ to 2^ 



in head ; 41 to 43 scales between lateral line and middle of back 



la. platessoides platessoides. 



B. Depth (2J) 2| to 3 in length ; maxdlary 2J- to 2 f, lower jaw i § to 2 in head ; 



25 to 40 scales between lateral Une and middle of back 



16. platessoides liinandoides. 

 II. 7 branchiostegal rays ; lateral hne generally with a low curve above 

 pectoral (sometimes nearly straight) ; contours of posterior parts of 

 dorsal and anal fins more or less concave ; praemaxillary teeth rather 

 stronger [Pacific species]. 



A. Dorsal about 8o-go, anal about 60-70; 12 to 19 gill-rakers on lower 



part of anterior arch. 



1. (14) 15 to 19 gUI-rakers ; canine teeth moderately developed ; outhne 



of upper jaw evenly curved ..... 2. elassodon. 



2. (II) 13 to 15 (16) gili-rakers ; canine teeth strongly developed ; outUne 



of upper jaw more strongly curved and irregular . . .3. dubius. 



B. Dorsal about 70-80 ; anal about 50-60 ; 10 to 13 gill-rakers on lower 



part of anterior arch ....... 4. robustus. 



I have followed Schmidt (1915) in recognising only three forms from the North 

 Pacific, but prefer to regard these, provisionally at any rate, as species rather than 

 subspecies. As Hubbs (1918) has pointed out, there is as yet no evidence that these 

 forms occupy different geographical areas, nor hais any intergradation been demon- 

 strated in the areas where their ranges overlap. The distinctions between robustus, 

 hamiltoni and propinqtius — depth of body, length of pectoral fin, form of the scales, 

 etc. — are of very doubtful value, especially when the differences in the sizes of the 

 specimens are taken into consideration. 



I. HIPPOGLOSSOIDES PL.\TESSOIDES (Fabricius). 



[Synonomy under Subspecies']. 



Depth of body 2j to 3 in the length, length of head 3 to 4^. Snout as long as or 

 shorter than eye, diameter of which is 3J to 5J in length of head ; anterior margins of 

 eyes about level. Maxillary extending to below middle of eye or a little beyond, length 

 2j to nearly 3 in that of head ; lower jaw a little projecting, i f to 2j in head ; anterior 

 teeth of upper jaw not greatly enlarged, not forming distinct canines. 8 branchio- 

 stegal rays ; 9 to 12 gill-rakers on lower part of anterior arch. Scales ctenoid on 



