8o A HISTORY OF FISHES 



but the loss of vision is amply compensated for by the sensitive 

 feelers formed by the rays of the pectoral and pelvic fins 

 In the Perch-like Cirrhitids or Firm-fins (Cirrhitidae) , of which 

 the Australian Trumpeter {Latris) is perhaps best known, 

 the lower rays of the pectorals are simple, thickened, free at 

 their tips, and sometimes more or less prolonged; here, again, 

 they act as sensory organs, and probably aid the fishes in their 

 search for food (Fig. 34h). 



The Gurnards (Trigla) and Sea Robins [Prionotus) have two 

 or three of the lower rays of the pectoral fins detached from the 

 remainder and modified to form stout finger-Hke appendages 

 (Fig. 34m). These are used for turning over sand or stones, 

 exploring shells, and otherwise searching for food, but also 

 serve a locomotor purpose, the appendages acting as limbs, 

 forward movement being produced by placing the tips of the 

 rays in contact with the sand and pushing backwards. In the 

 Flying Gurnard [Dactylopterus) the upper wing-like portion of 

 the pectoral is used for parachuting, and the lower part, as well 

 as the long thin pelvic fin, for creeping about on the sea floor. 

 According to Dr. Beebe, the pelvic leg-like fins work alternately, 

 one after the other. 



Coming, finally, to the pelvic or ventral fins, corresponding to 

 the legs of land vertebrates, it may be noted that, unhke the 

 pectorals, their position varies considerably in the different 

 groups of fishes, and is of some importance in classification. 

 In all the Selachians, and in the lower kinds of Bony Fishes, 

 such as the Fierring (Clupea), Salmon {Salmo)^ and Carp 

 (Cyprinus), the pelvics are placed in the middle of the belly 

 between the pectorals and the anal, and are said to be abdominal 

 in position (Figs. 13B, c). In other Bony Fishes, of which the 

 Perch (Perca), Bass (Morone), and Mackerel (Scomber) will serve 

 as examples, they are thoracic in position ; that is to say, they lie 

 farther forward in the region of the chest and more or less 

 below the pectorals (Figs. 5A; 34c, e). In others, again, such 

 as the Cods [Gadidae) and certain of the Blennies (Blennioidea), 

 they are described as jugular in position, and actually lie in 

 front of the pectorals in the region of the throat (Fig. 28b). 

 In a number of Bony Fishes, and particularly in those forms 

 which spend most of their time in burrowing, these fins are 

 either very much reduced in size or are wanting altogether. 

 All the living members of the order of Eeis (Apodes) are without 

 pelvics, but these have undoubtedly been derived from fishes 

 which possessed a full set of fins, confirmation of this view being 



