ÖFVERSIGT AF K. VETENSK.-AKAD. FÖRHANDLINGAR 1894, N:0 10. 585 



the plaice. The exceedingly small size of the pectoral fin in the 

 intermediate form ought to be observed, ^ it is smaller than in 

 any of the other Scandinavian flounders and thus must be re- 

 garded as anomalous. ^) Of other measurements there is none 

 that speaks against hybridisation having possibly taken place, 

 but if it has done so the product has been raore similar to the 

 plaice. This is, above all, the case with regard to the shape of 

 the head, and the eyes (herein lies also its great variation from 

 Pl. cynoglossus, in regard to the postorbital length). The eyes 

 of Pleuronectes cynoglossus are very much larger but less pro- 

 minent than in the intermediate form and the plaice. For in- 

 - stance, the length of the eye is contained but 8^/2 tiraes in the 

 length of head in Pleuronectes cynoglossus, but about 6 times 

 in the intermediate form and the plaice. The lips are very 

 thick in the two latter ones, but rather thin in Pleuronectes 

 cynoglossus, the nostrils of the eyeside are situated in a groove 

 between the eyes and snout. In the plaice and the intermediate 

 form no such groove is to be seen. The scales of the inter- 

 mediate form are very much larger than in a true plaice and 

 they are more regularly arranged in rows, but they are not im- 

 bricated as in the pole. The number of rays of dorsal and anal 

 fins in the intermediate form is not larger than it can be, and 

 usually is, in a plaice, a fact which strougly speaks against its 

 being a bastard, having the pole as one of its parent forms. 

 Taking all things into account it does not seem possible that 

 this form is a cross between the plaice and the pole, but any- 

 how, it is a most striking and highly interesting variety. The 

 smaller size of the head and the smaller depth of the body are 

 both juvenile characteristics, as is also the smaller mouth. The 

 larger scales may probably also be regarded as an atavistic 

 characteristic and thus, all taken together, we may possibly 

 regard this form as a product of atavisra, and then, at the 

 same time, its resemblance to other forms would be explained. 



Its shape resembles more that of the plaice than that of the pole as it is 

 rather rounded and not pointed. 



