Bd. V: 6) THE FISHES OF THE SWEDISH SOUTH POLAR EXPEDITION. 47 



5. Chaenichthys rhinoceratus RICHARDSON n. subsp. hamatus. 



I specimen, stat. 6, S. of Snow Hill, depth 125 m., stone and gravel. 20th of 

 Jan. igo2. 



It was of very great interest to find this fish among the collections of the 

 Swedish South Polar Expedition as it hitherto was known only from the coast of 

 Kerguelen Land, where it first was discovered by Sir jAMES Ross' expedition with 

 "Erebus" and "Terror" and described by RICHARDSON* 1844. The known dis- 

 tribution of this remarkable species of fish was through this later find extended to 

 nearly one half of the Antarctic region. But on the other hand, there are facts that 

 speak for the supposition that this distribution is discontinuous. There are namely 

 some differences between the description and figure of Richardson's type of Chœn- 

 ichthys rhinoceratus and this fish from Snow Hill. The most conspicuous at the first 

 look is the different shape of the first dorsal. In the original type the longest ray 

 of the first dorsal is the second, then resp. the third, fourth, first, fifth, sixth and 

 seventh. In consequence of this and the rapid decrease in size of the four hind- 

 most rays Richardson could term the first dorsal of this fish "high and triangular". 

 In the specimen from Snow Hill the order of the rays of the first dorsal according to 

 size is as follows: 4 — 3 — 2 = 5 — i — 6 — 7. This order, and the fact, that the sixth 

 ray only, is by '/s shorter than the first and that only by '/»s shorter than the equal 

 second and fifth, give quite a different shape to the first dorsal of the ChcenichtJiys 

 from Snow Hill. The number of rays in the second dorsal was 35 in the original 

 type, but in the present specimen 37. In a similar way the latter has an increased 

 number of rays in the anal fin as well viz. 33, while the type had only 30. The 

 pectoral of the former has 23 rays, that of the latter had only 20 according to the 

 description. But this may be a mistake as the figure exhibits 23 pectoral rays and 

 32 anal rays. More important is the difference with regard to the preopercle. 

 Richardson says that the same in the type "has an obtuse process, or elbow, a 

 little above the apex of the curve". But in the fish from Snow Hill the said bone 

 has at the angle of the curve two short but stout and pointed spines. This charac- 

 teristic has made me propose the name "hamatus" for the geographic race or sub- 

 species which appears to be represented by the fish from Snow Hill and which differs 

 from the type through the characteristics mentioned above. 



The total length of the specimen from Snow Hill is about 33 cm. without caudal, 

 and its colour is said to have been "bluish grey on the back and the sides". 



* Ichthyology of the Voyage of H. M. S. Erebus & Terror. 



