Bd. V: 6) THE FISHES OF THE SWEDISH SOUTH POLAR EXPEDITION. 21 



therefore might sometimes appear as an atavistic feature, and for that reason such a 

 characteristic cannot suffice to distinguish two species or subspecies of Ilucococtes. 

 but taken together with others it is of importance. And it is in this case not only 

 different colouration but differences with regard to the relative dimensions as well, 

 by which the present specimen is to be distinguished from Ilucocoetes fimbriatus, as 

 it is described in the literature, and from a specimen obtained by this expedition at 

 Tierra del Fuego, stat. 60 as well. The description of the present specimen is as 

 follows. 



Length of head fully 5 times in total length. Depth of body about three fourths 

 of the length of head and more than 7 times in total length. Snout longer than 

 the diameter of the eye (about 7s of the latter). Eye and interorbital space about 

 equal, contained about 53/5 times in length of head. The maxillary seems to ex- 

 tend to below the middle of the eye. A rather broad cutaneous flap at the corner 

 of the mouth, two more between the same and the nasal tube, and a median 

 one between both nasal tubes. Below the lower jaw three cutaneous appendages 

 alternate with large mucous pores on either side. Both upper and lower lips are 

 "fleshy" and folded. The dorsal begins in front of the extremity of the opercle. 

 Pectoral contained about i^^U times in length of head. Distance from base of pec- 

 toral to vent about 1V3 as long as head. Ventrals short, contained about 7 times 

 in head or 4 times in pectoral. 



From this is apparent that this form differs from the typical I. finibriatiis through 

 its longer snout and smaller eye, shorter ventrals and especially by the much greater 

 distance between base of pectoral and vent. The typical /. ßtiibriatiis is also said 

 to be of a uniform colouration. 



Steindachner has used the same name for a fish from eastern Tierra del 

 Fuego collected by Plate,* but the relative dimensions etc. of that fish differ so 

 much from the corresponding ones recorded for /. fimbriatus that it seems rather 

 uncertain whether the identification is correct. On the other hand it must be ad- 

 mitted that Steind.\CHNER's specimen is rather large, measuring about 252 mm. 

 and it is not known in this genus, how the relative dimensions are altered during 

 the growth. Steindachner's specimen has a much smaller head and eye and this 

 may be due to greater age. 



The differences between this transversely banded Ilucocoetes and the specimen 

 from Tierra del Fuego collected by this same expedition cannot be explained as 

 depending upon different age as both are young and nearly of the same size. The 

 following table of comparative measurements may therefore prove the existence of 

 more than one form of Ilucocoetes. 



* Die Fische der Sammlung Pl.ite, Fauna Chilensis, Hft 2 Zool. Jahrb. Suppl. 1898. 



